The study of magnetic field effects on the clock transition of Mg and Cd optical lattice clocks is scarce.In this work,the hyperfine-induced Landég-factors and quadratic Zeeman shift coefficients of the nsnp ^(3)...The study of magnetic field effects on the clock transition of Mg and Cd optical lattice clocks is scarce.In this work,the hyperfine-induced Landég-factors and quadratic Zeeman shift coefficients of the nsnp ^(3)P_(0)^(o) clock states for ^(111,113)Cd and ^(25)Mg were calculated by using the multi-configuration Dirac–Hartree–Fock theory.To obtain accurate values of these parameters,the impact of electron correlations and furthermore the Breit interaction and quantum electrodynamical effects on the Zeeman and hyperfine interaction matrix elements,and energy separations were investigated in detail.We also estimated the contributions from perturbing states to the Landég-factors and quadratic Zeeman shift coefficients concerned so as to truncate the summation over the perturbing states without loss of accuracy.Our calculations provide important data for estimating the first-and second-order Zeeman shifts of the clock transition for the Cd and Mg optical lattice clocks.展开更多
We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock p...We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.展开更多
We report on frequency measurement of the intercombination（5s^2）^1S0–（5s5p）^3P1transition of the four natural isotopes of strontium, including88^Sr（82.58%）,87^Sr（7.0%）,86^Sr（9.86%）, and84^Sr（0.56%）. A nar...We report on frequency measurement of the intercombination（5s^2）^1S0–（5s5p）^3P1transition of the four natural isotopes of strontium, including88^Sr（82.58%）,87^Sr（7.0%）,86^Sr（9.86%）, and84^Sr（0.56%）. A narrow-linewidth laser that is locked to an ultra-low expansion（ULE） optical cavity with a finesse of 12000 is evaluated at a linewidth of 200 Hz with a fractional frequency drift of 2.8×10^-13 at an integration time of 1 s. The fluorescence collector and detector are specially designed, based on a thermal atomic beam. Using a double-pass acousto-optic modulator（AOM） combined with a fiber and laser power stabilization configuration to detune the laser frequency enables high signal-to-noise ratios and precision saturated spectra to be obtained for the six transition lines, which allows us to determine the transition frequency precisely.The optical frequency is measured using an optical frequency synthesizer referenced to an H maser. Both the statistical values and the final values, including the corrections and uncertainties, are derived for a comparison with the values given in other works.展开更多
The discovery of the momentum space crystal based on the alkaline-earth atom ^(88)Sr in narrow-line cooling has paved the way to explore this novel physical phenomenon in other cold atom systems. In this paper, a mome...The discovery of the momentum space crystal based on the alkaline-earth atom ^(88)Sr in narrow-line cooling has paved the way to explore this novel physical phenomenon in other cold atom systems. In this paper, a momentum space crystal based on the fermions ^(87)Sr in narrow-line cooling of transition^1S_0–~3P_1 is demonstrated. We theoretically analyze and compare the formation principle of the narrow-line with that of broad-line cooling, and achieve the momentum space crystal in experiment. Beyond that we present a series of numerical calculations of those important parameters which influence the distribution and size of the momentum space crystal. Correspondingly, we vary the values of these parameters in experiment to observe the momentum space crystal evolution and distribution. The experimental results are in conformity with the results of the theoretically numerical calculations. These results and analyses provide a detailed supplementary study on the formation and evolution of momentum space crystal. In addition, this work could also give a guideline on atomic manipulation by narrow-line cooling.展开更多
We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in th...We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the ^87Sr optical lattice clock. The Zeeman shift of the 5 s5 p ^3 P0-5 s^2 ^1 S0 forbidden transition is measured with the π-polarized and σ^±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ^±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5 s^2 ^1 S0 g-factor for the ^87Sr atom is-1.306（52） ×10^-4, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factorδg between the 5 s5 p^3 P0 state and the 5 s^2 ^1 S0 state of the ^87Sr atoms is measured in the experiment as well,which are-7.67（36） ×10^-5 with π-transition spectra and-7.72（43） X 10^-5 with σ^±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76（2007） 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.展开更多
We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830...We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830_(-240)^(+600)s,measured using the magneto-optical trap as a photon amplifier to detect the weak decay events, is approximately60% larger than the previous experimental value τ = 520_(-140)^(+310)s. By considering the electron correlation effects in the framework of the multiconfiguration Dirac–Hartree–Fock theory, we obtained a theoretical lifetime of 1079(54) s, which lies in the range of measurements with error bars. Furthermore, we considered the higher-order electron correlation and Breit interaction to control the uncertainty of the theoretical calculation. The significant improvement in the agreement between calculations and measurements is attributed to the updated blackbody radiation-induced decay rate.展开更多
In the weak-magnetic-field approximation,we derived an expression of quadratic Zeeman shift coefficient of^(3)P_(0)^(o)clock state for^(88)Sr and^(87)Sr atoms.By using this formula and the multi-configuration Dirac-Ha...In the weak-magnetic-field approximation,we derived an expression of quadratic Zeeman shift coefficient of^(3)P_(0)^(o)clock state for^(88)Sr and^(87)Sr atoms.By using this formula and the multi-configuration Dirac-Hartree-Fock theory,the quadratic Zeeman shift coefficients were calculated.The calculated values C_(2)=-23.38(5)MHz/T^(2) for^(88)Sr and the^(3)p_(0)^(o),F=9/2,M_(F)=±9/2 clock states for^(87)Sr agree well with the other available theoretical and experimental values,especially the most accurate measurement recently.In addition,the calculated values of the^(3)p_(0)^(o),F=9/2,M_(F)=±9/2 clock states were also determined in our^(87)Sr optical lattice clock.The consistency with measurements verifies the validation of our calculation model.Our theory is also useful to evaluate the second-order Zeeman shift of the clock transition,for example,the new proposed^(1)S_(0),F=9/2,M_(F)=±5/2-^(3)P_(0)^(o),F=9/2,M_(F)=±3/2 transitions.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.61775220)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB21030100)the Key Research Project of Frontier Science of the Chinese Academy of Sciences (Grant No.QYZDB-SSW-JSC004)。
文摘The study of magnetic field effects on the clock transition of Mg and Cd optical lattice clocks is scarce.In this work,the hyperfine-induced Landég-factors and quadratic Zeeman shift coefficients of the nsnp ^(3)P_(0)^(o) clock states for ^(111,113)Cd and ^(25)Mg were calculated by using the multi-configuration Dirac–Hartree–Fock theory.To obtain accurate values of these parameters,the impact of electron correlations and furthermore the Breit interaction and quantum electrodynamical effects on the Zeeman and hyperfine interaction matrix elements,and energy separations were investigated in detail.We also estimated the contributions from perturbing states to the Landég-factors and quadratic Zeeman shift coefficients concerned so as to truncate the summation over the perturbing states without loss of accuracy.Our calculations provide important data for estimating the first-and second-order Zeeman shifts of the clock transition for the Cd and Mg optical lattice clocks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474282 and 61775220)the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030700)
文摘We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.
基金Project supported by the National Natural Science Foundation of China(Grant No.61127901)the Key Project of the Chinese Academy of Sciences(Grant No.KJZD-EW-W02)
文摘We report on frequency measurement of the intercombination（5s^2）^1S0–（5s5p）^3P1transition of the four natural isotopes of strontium, including88^Sr（82.58%）,87^Sr（7.0%）,86^Sr（9.86%）, and84^Sr（0.56%）. A narrow-linewidth laser that is locked to an ultra-low expansion（ULE） optical cavity with a finesse of 12000 is evaluated at a linewidth of 200 Hz with a fractional frequency drift of 2.8×10^-13 at an integration time of 1 s. The fluorescence collector and detector are specially designed, based on a thermal atomic beam. Using a double-pass acousto-optic modulator（AOM） combined with a fiber and laser power stabilization configuration to detune the laser frequency enables high signal-to-noise ratios and precision saturated spectra to be obtained for the six transition lines, which allows us to determine the transition frequency precisely.The optical frequency is measured using an optical frequency synthesizer referenced to an H maser. Both the statistical values and the final values, including the corrections and uncertainties, are derived for a comparison with the values given in other works.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474282 and 61775220)the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)
文摘The discovery of the momentum space crystal based on the alkaline-earth atom ^(88)Sr in narrow-line cooling has paved the way to explore this novel physical phenomenon in other cold atom systems. In this paper, a momentum space crystal based on the fermions ^(87)Sr in narrow-line cooling of transition^1S_0–~3P_1 is demonstrated. We theoretically analyze and compare the formation principle of the narrow-line with that of broad-line cooling, and achieve the momentum space crystal in experiment. Beyond that we present a series of numerical calculations of those important parameters which influence the distribution and size of the momentum space crystal. Correspondingly, we vary the values of these parameters in experiment to observe the momentum space crystal evolution and distribution. The experimental results are in conformity with the results of the theoretically numerical calculations. These results and analyses provide a detailed supplementary study on the formation and evolution of momentum space crystal. In addition, this work could also give a guideline on atomic manipulation by narrow-line cooling.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61127901,11404025 and 91536106the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB21030700+1 种基金the Key Research Project of Frontier Science of Chinese Academy of Sciences under Grant No QYZDB-SSW-JSC004the China Postdoctoral Science Foundation under Grant No 2014M560061
文摘We present an experimental determination on the Lande g-factors for the 5 s^2 ^1 S0 and 5 s5 p ^3P0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the ^87Sr optical lattice clock. The Zeeman shift of the 5 s5 p ^3 P0-5 s^2 ^1 S0 forbidden transition is measured with the π-polarized and σ^±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ^±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5 s^2 ^1 S0 g-factor for the ^87Sr atom is-1.306（52） ×10^-4, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factorδg between the 5 s5 p^3 P0 state and the 5 s^2 ^1 S0 state of the ^87Sr atoms is measured in the experiment as well,which are-7.67（36） ×10^-5 with π-transition spectra and-7.72（43） X 10^-5 with σ^±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76（2007） 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11874090, 91536106, 61127901, 11404025, and U1530142)the Strategic Priority Research Program of CAS (Grant No. XDB21030100)+1 种基金the Key Research Project of Frontier Science of CAS (Grant No. QYZDB-SSW-JSC004)the West Light Foundation of CAS (Grant No. XAB2018B17)。
文摘We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830_(-240)^(+600)s,measured using the magneto-optical trap as a photon amplifier to detect the weak decay events, is approximately60% larger than the previous experimental value τ = 520_(-140)^(+310)s. By considering the electron correlation effects in the framework of the multiconfiguration Dirac–Hartree–Fock theory, we obtained a theoretical lifetime of 1079(54) s, which lies in the range of measurements with error bars. Furthermore, we considered the higher-order electron correlation and Breit interaction to control the uncertainty of the theoretical calculation. The significant improvement in the agreement between calculations and measurements is attributed to the updated blackbody radiation-induced decay rate.
基金Project supported by the National Natural Science Foundation of China(Grant No.61775220)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)+1 种基金the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC004)the West Light Foundation of the Chinese Academy of Sciences(Grant No.XAB2018B17)。
文摘In the weak-magnetic-field approximation,we derived an expression of quadratic Zeeman shift coefficient of^(3)P_(0)^(o)clock state for^(88)Sr and^(87)Sr atoms.By using this formula and the multi-configuration Dirac-Hartree-Fock theory,the quadratic Zeeman shift coefficients were calculated.The calculated values C_(2)=-23.38(5)MHz/T^(2) for^(88)Sr and the^(3)p_(0)^(o),F=9/2,M_(F)=±9/2 clock states for^(87)Sr agree well with the other available theoretical and experimental values,especially the most accurate measurement recently.In addition,the calculated values of the^(3)p_(0)^(o),F=9/2,M_(F)=±9/2 clock states were also determined in our^(87)Sr optical lattice clock.The consistency with measurements verifies the validation of our calculation model.Our theory is also useful to evaluate the second-order Zeeman shift of the clock transition,for example,the new proposed^(1)S_(0),F=9/2,M_(F)=±5/2-^(3)P_(0)^(o),F=9/2,M_(F)=±3/2 transitions.
