Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization d...Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f76s6p[8Ph/2], 4f76s6p[8P7/2] and 4f76s6p[SP9/2] intermediate states, respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000 cm-1 to 38250 cm-1 and from 38900 cm-1 to 39500 cm-1. The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n* for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.展开更多
An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400-43500 cm^-1 is ...An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400-43500 cm^-1 is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f^76pnl(l = 0, 2) configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy (RIS) approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.展开更多
The radiative lifetimes of the Eu 4f76snp(8^PJ or10^PJ) Rydberg states with J = 5/2 and 11/2 are investigated with a combination of multi-step laser excitation and pulsed electric field ionization, from which their ...The radiative lifetimes of the Eu 4f76snp(8^PJ or10^PJ) Rydberg states with J = 5/2 and 11/2 are investigated with a combination of multi-step laser excitation and pulsed electric field ionization, from which their dependence on the effective principal quantum number is observed. The lifetimes of 21 states are reported along with an evaluation of their experimental uncertainty. The influence of blackbody radiation, due to the oven temperature, on the lifetime of the higher-n states is detected. The non-hydrogen behavior of the investigated states is also observed.展开更多
The field ionization process of the Eu 4f76snp Rydberg states, converging to the first ionization limit, 4f76s 954, is systematically investigated. The spectra of the Eu 4f76snp Rydberg states are populated with three...The field ionization process of the Eu 4f76snp Rydberg states, converging to the first ionization limit, 4f76s 954, is systematically investigated. The spectra of the Eu 4f76snp Rydberg states are populated with three-step laser excitation, and detected by electric field ionization (EFI) method. Two different kinds of the EFI pulses are applied after laser excitation to observe the possible impacts on the EFI process. The exact EFI ionization thresholds for the 4f76snp Rydberg states can be determined by observing the corresponding EFI spectra. In particular, some structures above the EFI threshold are found in the EFI spectra, which may be interpreted as the effect from black body radiation (BBR). Finally, the scaling law of the EFI threshold for the Eu 4f76snp Rydberg states with the effective quantum number is built.展开更多
The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large ...The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.展开更多
This paper analyzes the energy levels along the even-parity J = 1 and 2 Rydberg series of Sn I by multichannel quantum defect theory. A good agreement between theoretical and experimental energy levels was achieved. B...This paper analyzes the energy levels along the even-parity J = 1 and 2 Rydberg series of Sn I by multichannel quantum defect theory. A good agreement between theoretical and experimental energy levels was achieved. Below 59198 cm^-1, a total of 85 and 23 new energy levels, respectively, in the J = 1 and J = 2 series, which cannot be measured previously by experiments, are predicted in this work. Based on the calculated admixture coefficients of each channel, interchannel interactions were discussed in detail. The results are helpful to understand the characteristics of configuration interaction among even-parity levels in Sn I.展开更多
We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy ofcircular Rydberg states of hydrogen atoms in the intermediate magnetic Geld.This scheme can produce high accuracye...We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy ofcircular Rydberg states of hydrogen atoms in the intermediate magnetic Geld.This scheme can produce high accuracyenergy levels and valid for an arbitrary magnetic field.Energy levels of hydrogen are presented for circular Rydbergstates with azimuthal quantum numbers \m\ = 10-70 as a function of magnetic field strengths ranging from zero to2.35 x 109 T.The variation of spatial distributions of electron probability densities with magnetic field strengths isdiscussed and competition between Coulomb and magnetic interactions is illustrated.展开更多
The frequency-tunable light,which was produced by using YAG laser to pump the dye rhodamine 590/610,was used to measure the ions number in ionization of the benzene molecules Rydberg state 5Rg|10 as a function of the ...The frequency-tunable light,which was produced by using YAG laser to pump the dye rhodamine 590/610,was used to measure the ions number in ionization of the benzene molecules Rydberg state 5Rg|10 as a function of the light intensity.Fitting the measured data by using the deduced equation from the method of spatial integration,the ionization cross section of single photon of molecule benzene 5Rg|10 was obtained to be 2.1×10-19cm2 approximately.展开更多
Multiphoton resonant excitation and frustrated tunneling ionization,manifesting the photonic and optical nature of the driving light via direct excitation and electron recapture,respectively,are complementary mechanis...Multiphoton resonant excitation and frustrated tunneling ionization,manifesting the photonic and optical nature of the driving light via direct excitation and electron recapture,respectively,are complementary mechanisms to access Rydberg state excitation(RSE)of atoms and molecules in an intense laser field.However,clear identification and manipulation of their individual contributions in the light-induced RSE process remain experimentally challenging.Here,we bridge this gap by exploring the dissociative and nondissociative RSE of H2 molecules using bicircular two-color laser pulses.Depending on the relative field strength and polarization helicity of the two colors,the RSE probability can be boosted by more than one order of magnitude by exploiting the laser waveform-dependent field effect.The role of the photon effect is readily strengthened with increasing relative strength of the second-harmonic field of the two colors regardless of the polarization helicity.As compared to the nondissociative RSE forming H2,the field effect in producing the dissociative RSE channel of eHt;HT is moderately suppressed,which is primarily accessed via a three-step sequential process separated by molecular bond stretching.Our work paves the way toward a comprehensive understanding of the interplay of the underlying field and photon effects in the strong-field RSE process,as well as facilitating the generation of Rydberg states optimized with tailored characteristics.展开更多
The ionization processes of NH3 molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecu...The ionization processes of NH3 molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecules under different laser intensities are obtained. In the slow electron region, the values of kinetic energy of photoelectrons corresponding to peaks 1, 2, 3, and 4 are 0.27, 0.86, 1.16, and 1.6 eV, respectively. With both the kinetic energy and angular distribution of photoelectrons from NH3 molecules, we can confirm that the two-photon excited intermediate Rydberg state is A^1 A2" (v2'=3) state for photoelectron peaks 2, 3, 4, and the three peaks are marked as 1223 (2 + 2), 1123 (2 + 2), and 1023 (2 + 2) multi-photon processes, respectively. Then, peak 1 is found by adding a hexapole between the source chamber and the detection chamber to realize the rotational state selection and beam focusing. Peak 1 is labeled as the 1323 (3 + 1) multi-photon process through the intermediate Rydberg state E^1A1'. The phenomena of channel switching are found in the slow electron kinetic energy distributions. Our calculations and experimental results indicate that the stretching vibrational mode of ammonia molecules varies with channels, while the umbrella vibration does not. In addition, we consider and discuss the ac-Stark effect in a strong laser field. Peaks 5 and 6 are marked as (2 + 2 + 1) and (2 + 2 + 2) above threshold ionization processes in the fast electron region.展开更多
We calculate the Rydberg and autoionization Rydberg spectra of antimony (Sb) from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can ...We calculate the Rydberg and autoionization Rydberg spectra of antimony (Sb) from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can be used to classify and assign the atomic states described in recently reported three Rydberg series and four autoionizing states. The perturbation effects on line intensity, variation and line profile are discussed. Assignments of the perturber states and autoionizing states are presented.展开更多
Two-photon absorption in systems with parity permits access to states that cannot be directly prepared by one-photon absorption. Here we investigate ultrafast internal conversion (IC) dynamics of furan by using this...Two-photon absorption in systems with parity permits access to states that cannot be directly prepared by one-photon absorption. Here we investigate ultrafast internal conversion (IC) dynamics of furan by using this strategy in combination with femtosecond time-resolved photoelectron imaging. The dark Rydberg S1 and bright valence S2 states are simultaneously excited by two photons of 405 nm, and then ionized by two photons of 800nm. The IC from S2 to S1 is clearly observed and extracted from the time dependence of the higher photoelectron kinetic energy (PKE) component. More importantly, the internal conversions to hot So from directly-prepared S1 and secondarily-populated S1 are unambiguously identified by the time-dependence of the lower PKE component. The average lifetime of the S2 and S1 states is measured to be 29 fs. The internal conversions of S2 to S1, S1 to hot So occur on estimated timescales of 15.4 fs and 38 fs, respectively.展开更多
Laser induced photoemission electron was produced by directing 532 nm and/or 355 nm onto stainless steel plate on a time of flight mass spectrometer. Multiple charged ions and high Rydberg states of atoms or molecules...Laser induced photoemission electron was produced by directing 532 nm and/or 355 nm onto stainless steel plate on a time of flight mass spectrometer. Multiple charged ions and high Rydberg states of atoms or molecules were successfully generated by impacts of the photoemission electrons. The high Rydberg states ( n ~40-100) thus produced were separated from ions, produced by direct electron impact ionization, by a 3 V DC electric field and then ionized by a delayed pulsed HV electric field in a ZEKE-PFI manner. Relationship between generation/property of high Rydberg states of atoms/molecules and experimental conditions could be investigated. Relationship between the electron accelerating voltage and high Rydberg states of Ar was described.展开更多
(2+1) resonan multiphoton ionization of photolytically produced CH radical yields previously unobserved bands arising from two-photon transition to Rydberg states. Analysing of the spectrum of CH+, three new states ar...(2+1) resonan multiphoton ionization of photolytically produced CH radical yields previously unobserved bands arising from two-photon transition to Rydberg states. Analysing of the spectrum of CH+, three new states are identified. They are 8 d, 9 d and 10 d Rydberg states, respectively.展开更多
In this work, a three-step autoionization detection method and direct photoionization detection method are employed to measure the highly excited even-parity states of the Sm atom in the energy region between 36360 cm...In this work, a three-step autoionization detection method and direct photoionization detection method are employed to measure the highly excited even-parity states of the Sm atom in the energy region between 36360 cm^-1 and 40800 cm^-1. Comparisons between the results from the two detection techniques enable us to discriminate the Rydberg states from the valence states in the same energy region with the information of level energies, possible J values and their relative intensities. Furthermore, in the experiment two different excitation schemes are designed to obtain the spectra of highly excited even-parity states of the Sm atom. With a detailed analysis of the experimental data, this work not only confirms the results about many spectral data from the literature with different excitation schemes, but also reports new spectral data on 29 Rydberg states and 23 valence states.展开更多
We present nonlinear spectra of four-level ladder cesium atoms employing 6 S1/2→6 P3/2→7 S1/2→30 P3/2 scheme of a room temperature vapor cell.A coupling laser drives Rydberg transition,a dressing laser couples two ...We present nonlinear spectra of four-level ladder cesium atoms employing 6 S1/2→6 P3/2→7 S1/2→30 P3/2 scheme of a room temperature vapor cell.A coupling laser drives Rydberg transition,a dressing laser couples two intermediate levels,and a probe laser optically probes the nonlinear spectra via electromagnetically induced transparency(EIT).Nonlinear spectra are detected as a function of coupling laser frequency.The observed spectra exhibit an enhanced absorption(EA) signal at coupling laser resonance to Rydberg transition and enhanced transmission(ET) signals at detunings to the transition.We define the enhanced absorption(transmission) strength,HEA(HET),and distance between two ET peaks,γET,to describe the spectral feature of the four-level atoms.The enhanced absorption signal HEA is found to have a maximum value when we vary the dressing laser Rabi frequency Ωd,corresponding Rabi frequency is defined as a separatrix point,ΩdSe.The values of ΩdSe and further η=ΩdSe/Ωc are found to depend on the probe and coupling Rabi frequency but not the atomic density.Based on ΩdSe,the spectra can be separated into two regimes,weak and strong dressing ranges,Ωd≤ΩdSe and Ωd≥QdSe,respectively.The spectroscopies display different features at these two regimes.A four-level theoretical model is developed that agrees well with the experimental results in terms of the probe-beam absorption behavior of Rabi frequency-dependent dressed states.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574098, 10674102)the Natural Science Foundation of Tianjin (Grant No 05YFJMJC05200)
文摘Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f76s6p[8Ph/2], 4f76s6p[8P7/2] and 4f76s6p[SP9/2] intermediate states, respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000 cm-1 to 38250 cm-1 and from 38900 cm-1 to 39500 cm-1. The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n* for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10574098 and 10674102)the Natural Science Foundation of Tianjin,China (Grant No.05YFJMJC05200)
文摘An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400-43500 cm^-1 is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f^76pnl(l = 0, 2) configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy (RIS) approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174218)
文摘The radiative lifetimes of the Eu 4f76snp(8^PJ or10^PJ) Rydberg states with J = 5/2 and 11/2 are investigated with a combination of multi-step laser excitation and pulsed electric field ionization, from which their dependence on the effective principal quantum number is observed. The lifetimes of 21 states are reported along with an evaluation of their experimental uncertainty. The influence of blackbody radiation, due to the oven temperature, on the lifetime of the higher-n states is detected. The non-hydrogen behavior of the investigated states is also observed.
基金supported by the National Natural Science Foundation of China(Grant Nos.11004151 and 11174218)
文摘The field ionization process of the Eu 4f76snp Rydberg states, converging to the first ionization limit, 4f76s 954, is systematically investigated. The spectra of the Eu 4f76snp Rydberg states are populated with three-step laser excitation, and detected by electric field ionization (EFI) method. Two different kinds of the EFI pulses are applied after laser excitation to observe the possible impacts on the EFI process. The exact EFI ionization thresholds for the 4f76snp Rydberg states can be determined by observing the corresponding EFI spectra. In particular, some structures above the EFI threshold are found in the EFI spectra, which may be interpreted as the effect from black body radiation (BBR). Finally, the scaling law of the EFI threshold for the Eu 4f76snp Rydberg states with the effective quantum number is built.
基金the National Basic Research Program of China(Grant No.2012CB921603)the National Natural Science Foundation of China(Grant Nos.61078001,61178009,11274209,and 60778008)+2 种基金the Fund for Fostering Talents in Basic Science of the National Natural Science Foundation of China(Grant No.J1103210)the Natural Science Foundation of Shanxi Province,China(Grant No.2012011003-2)the Shanxi International Collaboration Program(Grant No.2010081046)
文摘The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574056)the Program for New Century Excellent Talents in University (China)
文摘This paper analyzes the energy levels along the even-parity J = 1 and 2 Rydberg series of Sn I by multichannel quantum defect theory. A good agreement between theoretical and experimental energy levels was achieved. Below 59198 cm^-1, a total of 85 and 23 new energy levels, respectively, in the J = 1 and J = 2 series, which cannot be measured previously by experiments, are predicted in this work. Based on the calculated admixture coefficients of each channel, interchannel interactions were discussed in detail. The results are helpful to understand the characteristics of configuration interaction among even-parity levels in Sn I.
基金Support from National Science Foundation of USA under Grant No. 0630370National Natural Science Foundation of China under Grant Nos. 90403028 and 11074260
文摘We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy ofcircular Rydberg states of hydrogen atoms in the intermediate magnetic Geld.This scheme can produce high accuracyenergy levels and valid for an arbitrary magnetic field.Energy levels of hydrogen are presented for circular Rydbergstates with azimuthal quantum numbers \m\ = 10-70 as a function of magnetic field strengths ranging from zero to2.35 x 109 T.The variation of spatial distributions of electron probability densities with magnetic field strengths isdiscussed and competition between Coulomb and magnetic interactions is illustrated.
文摘The frequency-tunable light,which was produced by using YAG laser to pump the dye rhodamine 590/610,was used to measure the ions number in ionization of the benzene molecules Rydberg state 5Rg|10 as a function of the light intensity.Fitting the measured data by using the deduced equation from the method of spatial integration,the ionization cross section of single photon of molecule benzene 5Rg|10 was obtained to be 2.1×10-19cm2 approximately.
基金the National Key R&D Program of China(Grant No.2018YFA0306303)the National Natural Science Foundation of China(Grant Nos.11834004,61690224,92150105,11904103,12241407,and 12227807)the Science and Technology Commission of Shanghai Municipality(Grant No.21ZR1420100).
文摘Multiphoton resonant excitation and frustrated tunneling ionization,manifesting the photonic and optical nature of the driving light via direct excitation and electron recapture,respectively,are complementary mechanisms to access Rydberg state excitation(RSE)of atoms and molecules in an intense laser field.However,clear identification and manipulation of their individual contributions in the light-induced RSE process remain experimentally challenging.Here,we bridge this gap by exploring the dissociative and nondissociative RSE of H2 molecules using bicircular two-color laser pulses.Depending on the relative field strength and polarization helicity of the two colors,the RSE probability can be boosted by more than one order of magnitude by exploiting the laser waveform-dependent field effect.The role of the photon effect is readily strengthened with increasing relative strength of the second-harmonic field of the two colors regardless of the polarization helicity.As compared to the nondissociative RSE forming H2,the field effect in producing the dissociative RSE channel of eHt;HT is moderately suppressed,which is primarily accessed via a three-step sequential process separated by molecular bond stretching.Our work paves the way toward a comprehensive understanding of the interplay of the underlying field and photon effects in the strong-field RSE process,as well as facilitating the generation of Rydberg states optimized with tailored characteristics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11574116, 11534004, and 10704028).
文摘The ionization processes of NH3 molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecules under different laser intensities are obtained. In the slow electron region, the values of kinetic energy of photoelectrons corresponding to peaks 1, 2, 3, and 4 are 0.27, 0.86, 1.16, and 1.6 eV, respectively. With both the kinetic energy and angular distribution of photoelectrons from NH3 molecules, we can confirm that the two-photon excited intermediate Rydberg state is A^1 A2" (v2'=3) state for photoelectron peaks 2, 3, 4, and the three peaks are marked as 1223 (2 + 2), 1123 (2 + 2), and 1023 (2 + 2) multi-photon processes, respectively. Then, peak 1 is found by adding a hexapole between the source chamber and the detection chamber to realize the rotational state selection and beam focusing. Peak 1 is labeled as the 1323 (3 + 1) multi-photon process through the intermediate Rydberg state E^1A1'. The phenomena of channel switching are found in the slow electron kinetic energy distributions. Our calculations and experimental results indicate that the stretching vibrational mode of ammonia molecules varies with channels, while the umbrella vibration does not. In addition, we consider and discuss the ac-Stark effect in a strong laser field. Peaks 5 and 6 are marked as (2 + 2 + 1) and (2 + 2 + 2) above threshold ionization processes in the fast electron region.
基金The project supported by National Natural Science Foundation of China under Grant No. 10274063 and the Foundation of Science and Technology Research of the Ministry of Education of China under Grant No. 03126
基金Supported by the Beijing Natural Science Foundation under Grant No 1164016the National Natural Science Foundation of China under Grant No 11604334the Funding from TRIUMF which receives Federal Funding via a Contribution Agreement with the National Research Council of Canada and through a Natural Sciences and Engineering Research Council of Canada under Grant No 386343-2011
文摘We calculate the Rydberg and autoionization Rydberg spectra of antimony (Sb) from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can be used to classify and assign the atomic states described in recently reported three Rydberg series and four autoionizing states. The perturbation effects on line intensity, variation and line profile are discussed. Assignments of the perturber states and autoionizing states are presented.
基金Supported by the National Natural Science Foundation of China under Grant Nos 21303255,21273274 and 91121006
文摘Two-photon absorption in systems with parity permits access to states that cannot be directly prepared by one-photon absorption. Here we investigate ultrafast internal conversion (IC) dynamics of furan by using this strategy in combination with femtosecond time-resolved photoelectron imaging. The dark Rydberg S1 and bright valence S2 states are simultaneously excited by two photons of 405 nm, and then ionized by two photons of 800nm. The IC from S2 to S1 is clearly observed and extracted from the time dependence of the higher photoelectron kinetic energy (PKE) component. More importantly, the internal conversions to hot So from directly-prepared S1 and secondarily-populated S1 are unambiguously identified by the time-dependence of the lower PKE component. The average lifetime of the S2 and S1 states is measured to be 29 fs. The internal conversions of S2 to S1, S1 to hot So occur on estimated timescales of 15.4 fs and 38 fs, respectively.
文摘Laser induced photoemission electron was produced by directing 532 nm and/or 355 nm onto stainless steel plate on a time of flight mass spectrometer. Multiple charged ions and high Rydberg states of atoms or molecules were successfully generated by impacts of the photoemission electrons. The high Rydberg states ( n ~40-100) thus produced were separated from ions, produced by direct electron impact ionization, by a 3 V DC electric field and then ionized by a delayed pulsed HV electric field in a ZEKE-PFI manner. Relationship between generation/property of high Rydberg states of atoms/molecules and experimental conditions could be investigated. Relationship between the electron accelerating voltage and high Rydberg states of Ar was described.
文摘(2+1) resonan multiphoton ionization of photolytically produced CH radical yields previously unobserved bands arising from two-photon transition to Rydberg states. Analysing of the spectrum of CH+, three new states are identified. They are 8 d, 9 d and 10 d Rydberg states, respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos 10574098 and 10674102)the Natural Science Foundation of Tianjin (Grant No 05YFJMJC05200)
文摘In this work, a three-step autoionization detection method and direct photoionization detection method are employed to measure the highly excited even-parity states of the Sm atom in the energy region between 36360 cm^-1 and 40800 cm^-1. Comparisons between the results from the two detection techniques enable us to discriminate the Rydberg states from the valence states in the same energy region with the information of level energies, possible J values and their relative intensities. Furthermore, in the experiment two different excitation schemes are designed to obtain the spectra of highly excited even-parity states of the Sm atom. With a detailed analysis of the experimental data, this work not only confirms the results about many spectral data from the literature with different excitation schemes, but also reports new spectral data on 29 Rydberg states and 23 valence states.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304203)the State Key Program of the National Natural Science of China(Grant Nos.11434007 and 61835007)+1 种基金the National Natural Science Foundation of China(Grant Nos.61675123,61775124,and 11804202)the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT 17R70).
文摘We present nonlinear spectra of four-level ladder cesium atoms employing 6 S1/2→6 P3/2→7 S1/2→30 P3/2 scheme of a room temperature vapor cell.A coupling laser drives Rydberg transition,a dressing laser couples two intermediate levels,and a probe laser optically probes the nonlinear spectra via electromagnetically induced transparency(EIT).Nonlinear spectra are detected as a function of coupling laser frequency.The observed spectra exhibit an enhanced absorption(EA) signal at coupling laser resonance to Rydberg transition and enhanced transmission(ET) signals at detunings to the transition.We define the enhanced absorption(transmission) strength,HEA(HET),and distance between two ET peaks,γET,to describe the spectral feature of the four-level atoms.The enhanced absorption signal HEA is found to have a maximum value when we vary the dressing laser Rabi frequency Ωd,corresponding Rabi frequency is defined as a separatrix point,ΩdSe.The values of ΩdSe and further η=ΩdSe/Ωc are found to depend on the probe and coupling Rabi frequency but not the atomic density.Based on ΩdSe,the spectra can be separated into two regimes,weak and strong dressing ranges,Ωd≤ΩdSe and Ωd≥QdSe,respectively.The spectroscopies display different features at these two regimes.A four-level theoretical model is developed that agrees well with the experimental results in terms of the probe-beam absorption behavior of Rabi frequency-dependent dressed states.