Coherent optical emission of free induction decay (FID) excited by the multiple-photon resonance has been recently observed in nitrogen ions produced by intense femtosecond laser pulses.Here we report that orbit angul...Coherent optical emission of free induction decay (FID) excited by the multiple-photon resonance has been recently observed in nitrogen ions produced by intense femtosecond laser pulses.Here we report that orbit angular momentum (OAM) of the pump laser pulses can be transferred to the much longer pulsed free induction decay emission with the OAM conserved.It was found that when the pump laser frequency approaches the fraction of the 391.4 nm emission (ν_(0)/5),an FID emission is emitted whereas its topological charge was identified to be 5 times of the pump laser.Due to the reduced laser intensity with a vortex pump compared to the conventional Gaussian beam,the resonant pump laser wavelength presents a redshift,and the FID signal is significantly weaker.展开更多
Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxatio...Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T_(2)) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T_(2) is conducive to further improvement of gyroscope. At present, for the measurement of T_(2), the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T_(2) by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T_(2) of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance.展开更多
We present a comparative study on the C-H stretching vibrations at air/DMSO （dimethyl sulfoxide） interface with both the free-induction decay （FID） coherent vibrational dynamics and the sub-wavenumber high resolut...We present a comparative study on the C-H stretching vibrations at air/DMSO （dimethyl sulfoxide） interface with both the free-induction decay （FID） coherent vibrational dynamics and the sub-wavenumber high resolution sum-frequency generation vibrational spectroscopy measurements. In principle the frequency-domain and time-domain spectroscopic measurements should generate identical information for a given molecular system. However, when the molecular systems are with several coupled or overlapping vibrational modes, obtain- ing detailed spectroscopic and coherent dynamics information is not as straightforward and rather difficult from either the time-domain or the frequency domain measurements. For the case of air/DMSO interface that is with moderately complex vibrational spectra, we show that the frequency-domain measurement with sub-wavenumber high-resolution sum-frequency generation vibrational spectroscopy is probably more advantageous than the time- domain measurement in obtaining quantitative understanding of the structure and coherent dynamics of the molecular interface.展开更多
利用时域核磁共振(TD-NMR)技术,为研究人造板和水分的关系提供新方法.该文通过研究胶合板(Plywood)、刨花板(Particle board)、中密度纤维板(Medium Density Fiberboard)3种常用人造板吸水过程中水分的自由感应衰减(FID)信号的变化,得...利用时域核磁共振(TD-NMR)技术,为研究人造板和水分的关系提供新方法.该文通过研究胶合板(Plywood)、刨花板(Particle board)、中密度纤维板(Medium Density Fiberboard)3种常用人造板吸水过程中水分的自由感应衰减(FID)信号的变化,得出传统称重法得到的吸水率与吸水过程中测得的FID信号高度线性相关,24 h吸水率由大到小依次为胶合板>刨花板>中密度纤维板.通过3种人造板24 h吸水过程中自旋-自旋弛豫时间(T2)大小及分布的实验数据,分析了吸水过程中人造板中水分的状态.实验结果证实了TD-NMR是研究人造板与水分的关系的一个有效手段.展开更多
基金supported in part by the National Natural Science Foundation of China (Nos.12034013 and 12204308)the Shanghai Science and Technology Commission (No.22ZR1444100)。
文摘Coherent optical emission of free induction decay (FID) excited by the multiple-photon resonance has been recently observed in nitrogen ions produced by intense femtosecond laser pulses.Here we report that orbit angular momentum (OAM) of the pump laser pulses can be transferred to the much longer pulsed free induction decay emission with the OAM conserved.It was found that when the pump laser frequency approaches the fraction of the 391.4 nm emission (ν_(0)/5),an FID emission is emitted whereas its topological charge was identified to be 5 times of the pump laser.Due to the reduced laser intensity with a vortex pump compared to the conventional Gaussian beam,the resonant pump laser wavelength presents a redshift,and the FID signal is significantly weaker.
基金the Shanghai Aerospace Advanced Technology Joint Research Fund(No.USCAST2019-23)。
文摘Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T_(2)) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T_(2) is conducive to further improvement of gyroscope. At present, for the measurement of T_(2), the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T_(2) by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T_(2) of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance.
文摘We present a comparative study on the C-H stretching vibrations at air/DMSO （dimethyl sulfoxide） interface with both the free-induction decay （FID） coherent vibrational dynamics and the sub-wavenumber high resolution sum-frequency generation vibrational spectroscopy measurements. In principle the frequency-domain and time-domain spectroscopic measurements should generate identical information for a given molecular system. However, when the molecular systems are with several coupled or overlapping vibrational modes, obtain- ing detailed spectroscopic and coherent dynamics information is not as straightforward and rather difficult from either the time-domain or the frequency domain measurements. For the case of air/DMSO interface that is with moderately complex vibrational spectra, we show that the frequency-domain measurement with sub-wavenumber high-resolution sum-frequency generation vibrational spectroscopy is probably more advantageous than the time- domain measurement in obtaining quantitative understanding of the structure and coherent dynamics of the molecular interface.
