The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO2+2 and CO3+2 is identified by the ion-ion coincidence- method using a momentum imaging spectromete...The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO2+2 and CO3+2 is identified by the ion-ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections (PICSs) of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system.展开更多
The field-ionization Coulomb explosion model is extended to investigate the multielectron dissociative ionization process of N2 molecule irradiated by an intense femtosecond laser field with an arbitrary polarization....The field-ionization Coulomb explosion model is extended to investigate the multielectron dissociative ionization process of N2 molecule irradiated by an intense femtosecond laser field with an arbitrary polarization. The ionization process of N2 molecule is found to be optimal at the critical internuclear distance Rc=7a.u., which is independent of the laser polarization state, the molecular explosion channel and the angle between the molecular axis and the direction of laser electric field. The kinetic energies of the ion fragments are identical in the cases of linear and circular polarizations at the same incident laser intensity. However, the probability of electron ionization is very sensitive to the above three parameters. At the critical distance Rc=7a.u. the angular dependence of the threshold intensity for the over-the-barrier ionization leads to the geometric alignment of molecules in the case of linear polarization. The threshold intensity in the case of circular polarization is apparently higher than that in the case of linear polarization, which can well explain the significant decrease of ionization in the case of circular polarization. The numerical calculations are compared with the experimental measurements.展开更多
Comprehension of photon-triggered molecular processes is essential in the study of various important topics in physics,chemistry,and biology.Here we propose a correlated tunneling picture to understand the dissociativ...Comprehension of photon-triggered molecular processes is essential in the study of various important topics in physics,chemistry,and biology.Here we propose a correlated tunneling picture to understand the dissociative ionization process of molecules in intense laser fields based on a quantum model developed in the framework of many-body S-matrix theory including nuclear vibrational motion.In this quantum correlation picture,the single ionization of H_(2)and the subsequent electron-ion recollisioninduced dissociation are considered as an entangled correlated process.It enables us to attribute the interference pattern in the joint-energy spectra to combined effects of single-slit diffraction and multi-slit interference of correlated electron-nuclear wave packets in the time domain.Our work opens a new avenue to understanding molecular dissociative ionization processes in external fields.展开更多
Ionization and dissociation of linear triatomic molecules, carbon dioxide, are studied in 50-fs 800-nm strong laser fields using time-of-flight mass spectrometer. The yields of double charged ions CO2^2+ and various ...Ionization and dissociation of linear triatomic molecules, carbon dioxide, are studied in 50-fs 800-nm strong laser fields using time-of-flight mass spectrometer. The yields of double charged ions CO2^2+ and various fragment ions(CO^+,O^n+, and C^n+(n = 1, 2)) are measured as a function of ellipticity of laser polarization in the intensity range from 5.0 ×10^13W/cm2 to 6.0 × 10^14W/cm^2. The results demonstrate that non-sequential double ionization, which is induced by laser-driven electron recollision, dominates double ionization of CO2 in the strong IR laser field with intensity lower than2.0 × 10^14W/cm^2. The electron recollision could also have contribution in strong-field multiple ionization and formation of fragments of CO2 molecules. The present study indicates that the intensity and ellipticity dependence of ions yields can be used to probe the complex dynamics of strong-field ionization/dissociation of polyatomic molecules.展开更多
Identification of acetone and its two isomers, and the control of their ionization and dissociation processes are performed using a dual-mass-spectrometer scheme. The scheme employs two sets of time of flight mass spe...Identification of acetone and its two isomers, and the control of their ionization and dissociation processes are performed using a dual-mass-spectrometer scheme. The scheme employs two sets of time of flight mass spectrometers to simultaneously acquire the mass spectra of two different molecules under the irradiation of identically shaped femtosecond laser pulses. The optimal laser pulses are found using closed-loop learning method based on a genetic algorithm. Compared with the mass spectra of the two isomers that are obtained with the transform limited pulse, those obtained under the irradiation of the optimal laser pulse show large differences and the various reaction pathways of the two molecules are selectively controlled. The experimental results demonstrate that the scheme is quite effective and useful in studies of two molecules having common mass peaks, which makes a traditional single mass spectrometer unfeasible.展开更多
This paper reports that a one-colour fs pump probe measurement has been carried out for studying photoionization/photodissociation of cyclohexanone (C6H10O) in intense laser field. Two of the fragments from eyclohex...This paper reports that a one-colour fs pump probe measurement has been carried out for studying photoionization/photodissociation of cyclohexanone (C6H10O) in intense laser field. Two of the fragments from eyclohexanone, C2H+ and C3H3+, are studied under 800 nm laser pump-probe and the results obtained show similar time evolutions. It proposes a feasible model for analysing the experimental observations of the one-colour fs pump-probe measurement. The results demonstrate that as an intermediate product, the excited molecular parent ions play a very important role in photionization/photodissociation processes in intense laser field.展开更多
We studied the ionization and dissociation of polyatomic molecule methane in an intense femtosecond laser field with wavelength of 810 nm and intensities ranging from 1.4 × 1014 to 2.6× 1015 W/cm2 by mass sp...We studied the ionization and dissociation of polyatomic molecule methane in an intense femtosecond laser field with wavelength of 810 nm and intensities ranging from 1.4 × 1014 to 2.6× 1015 W/cm2 by mass spectroscopy. Abundant fragment ions were observed in addition to the strong parent ion. The effect of frequency chirp was investigated and it was found that the negatively chirped pulses dramatically enhanced the dissociation probability, which might, be used to control the dissociation pathways.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
基金supported by the National Basic Research Program of China(Grant No.2010CB923301)the National Natural Science Foundation of China(Grant Nos.11327404,10979007,and 10734040)the Fundamental Research Funds for the Central Universities,China
文摘The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO2+2 and CO3+2 is identified by the ion-ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections (PICSs) of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system.
基金Project supported by the National Key Basic Research Special Foundation (NKBRSF) (Grant No TG1999075207) and the National Natural Science Foundation of China (Grant Nos 10104003, 90206003 and 60378012) and the China Postdoctoral Science Foundation (Grant No 2003034093).
文摘The field-ionization Coulomb explosion model is extended to investigate the multielectron dissociative ionization process of N2 molecule irradiated by an intense femtosecond laser field with an arbitrary polarization. The ionization process of N2 molecule is found to be optimal at the critical internuclear distance Rc=7a.u., which is independent of the laser polarization state, the molecular explosion channel and the angle between the molecular axis and the direction of laser electric field. The kinetic energies of the ion fragments are identical in the cases of linear and circular polarizations at the same incident laser intensity. However, the probability of electron ionization is very sensitive to the above three parameters. At the critical distance Rc=7a.u. the angular dependence of the threshold intensity for the over-the-barrier ionization leads to the geometric alignment of molecules in the case of linear polarization. The threshold intensity in the case of circular polarization is apparently higher than that in the case of linear polarization, which can well explain the significant decrease of ionization in the case of circular polarization. The numerical calculations are compared with the experimental measurements.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0307700)the National Natural Science Foundation of China(Grant Nos.12274273,12304379,11925405+2 种基金12304304)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302101)the Natural and Science Foundation of Top Talent of SZTU(Grant No.GDRC202202)。
文摘Comprehension of photon-triggered molecular processes is essential in the study of various important topics in physics,chemistry,and biology.Here we propose a correlated tunneling picture to understand the dissociative ionization process of molecules in intense laser fields based on a quantum model developed in the framework of many-body S-matrix theory including nuclear vibrational motion.In this quantum correlation picture,the single ionization of H_(2)and the subsequent electron-ion recollisioninduced dissociation are considered as an entangled correlated process.It enables us to attribute the interference pattern in the joint-energy spectra to combined effects of single-slit diffraction and multi-slit interference of correlated electron-nuclear wave packets in the time domain.Our work opens a new avenue to understanding molecular dissociative ionization processes in external fields.
基金supported by the National Basic Research Program of China(Grant No.2013CB922200)the National Natural Science Foundation of China(Grant Nos.11034003 and 11274140)
文摘Ionization and dissociation of linear triatomic molecules, carbon dioxide, are studied in 50-fs 800-nm strong laser fields using time-of-flight mass spectrometer. The yields of double charged ions CO2^2+ and various fragment ions(CO^+,O^n+, and C^n+(n = 1, 2)) are measured as a function of ellipticity of laser polarization in the intensity range from 5.0 ×10^13W/cm2 to 6.0 × 10^14W/cm^2. The results demonstrate that non-sequential double ionization, which is induced by laser-driven electron recollision, dominates double ionization of CO2 in the strong IR laser field with intensity lower than2.0 × 10^14W/cm^2. The electron recollision could also have contribution in strong-field multiple ionization and formation of fragments of CO2 molecules. The present study indicates that the intensity and ellipticity dependence of ions yields can be used to probe the complex dynamics of strong-field ionization/dissociation of polyatomic molecules.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922200)the National Natural Science Foundation of China(Grant No.11374124)
文摘Identification of acetone and its two isomers, and the control of their ionization and dissociation processes are performed using a dual-mass-spectrometer scheme. The scheme employs two sets of time of flight mass spectrometers to simultaneously acquire the mass spectra of two different molecules under the irradiation of identically shaped femtosecond laser pulses. The optimal laser pulses are found using closed-loop learning method based on a genetic algorithm. Compared with the mass spectra of the two isomers that are obtained with the transform limited pulse, those obtained under the irradiation of the optimal laser pulse show large differences and the various reaction pathways of the two molecules are selectively controlled. The experimental results demonstrate that the scheme is quite effective and useful in studies of two molecules having common mass peaks, which makes a traditional single mass spectrometer unfeasible.
基金Project supported by the National Natural Science Foundation of China (Grant No 10534010)
文摘This paper reports that a one-colour fs pump probe measurement has been carried out for studying photoionization/photodissociation of cyclohexanone (C6H10O) in intense laser field. Two of the fragments from eyclohexanone, C2H+ and C3H3+, are studied under 800 nm laser pump-probe and the results obtained show similar time evolutions. It proposes a feasible model for analysing the experimental observations of the one-colour fs pump-probe measurement. The results demonstrate that as an intermediate product, the excited molecular parent ions play a very important role in photionization/photodissociation processes in intense laser field.
基金This work was supported by the National Key Basic Research Special Foundation(NKBRSF)under Grant No.G1999075207the National Natural Science Foundation of China under Grant No.19884001,10104003 and 90101027.
文摘We studied the ionization and dissociation of polyatomic molecule methane in an intense femtosecond laser field with wavelength of 810 nm and intensities ranging from 1.4 × 1014 to 2.6× 1015 W/cm2 by mass spectroscopy. Abundant fragment ions were observed in addition to the strong parent ion. The effect of frequency chirp was investigated and it was found that the negatively chirped pulses dramatically enhanced the dissociation probability, which might, be used to control the dissociation pathways.
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.