Femtosecond time-resolved transient grating(TG) technique is used to study the intermolecular dynamics in liquid phase. Non-resonant excitation of the sample by two crossing laser pulses results in a transient Kerr gr...Femtosecond time-resolved transient grating(TG) technique is used to study the intermolecular dynamics in liquid phase. Non-resonant excitation of the sample by two crossing laser pulses results in a transient Kerr grating, and the molecular motion of liquid can be detected by monitoring the diffraction of a third time-delayed probe pulse. In liquid nitrobenzene(NB), three intermolecular processes are observed with lifetimes of 37.9±1.4 ps, 3.28±0.11 ps, and 0.44±0.03 ps, respectively. These relaxations are assigned to molecular orientational diffusion, dipole/induced dipole interaction, and libration in liquid cage, respectively. Such a result is slightly different from that obtained from OKE experiment in which the lifetime of the intermediate process is measured to be 1.9 ps. The effects of electric field on matter are different in TG and optical Kerr effect(OKE) experiments, which should be responsible for the difference between the results of these two types of experiments. The present work demonstrates that TG technique is a useful alternative in the study of intermolecular dynamics.展开更多
The structural deformation induced by intense laser field of liquid nitrobenzene（NB） molecule,a typical molecule with restricting internal rotation,is tracked by time- and frequency-resolved coherent anti-Stokes.Ram...The structural deformation induced by intense laser field of liquid nitrobenzene（NB） molecule,a typical molecule with restricting internal rotation,is tracked by time- and frequency-resolved coherent anti-Stokes.Raman spectroscopy（CARS） technique with an intense pump laser.The CARS spectra of liquid NB show that the NO2 torsional mode couples with the NO2 symmetric stretching mode,and the NB molecule undergoes ultrafast structural deformation with a relaxation time of 265 fs.The frequency of NO2 torsional mode in liquid NB（42 cm-1） at room temperature is found from the sum and difference combination bands involving the NO2 symmetric stretching mode and torsional mode in time- and frequency-resolved CARS spectra.展开更多
The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） tec...The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11304058 and 11404307)NSAF(Grant No.U1330106)
文摘Femtosecond time-resolved transient grating(TG) technique is used to study the intermolecular dynamics in liquid phase. Non-resonant excitation of the sample by two crossing laser pulses results in a transient Kerr grating, and the molecular motion of liquid can be detected by monitoring the diffraction of a third time-delayed probe pulse. In liquid nitrobenzene(NB), three intermolecular processes are observed with lifetimes of 37.9±1.4 ps, 3.28±0.11 ps, and 0.44±0.03 ps, respectively. These relaxations are assigned to molecular orientational diffusion, dipole/induced dipole interaction, and libration in liquid cage, respectively. Such a result is slightly different from that obtained from OKE experiment in which the lifetime of the intermediate process is measured to be 1.9 ps. The effects of electric field on matter are different in TG and optical Kerr effect(OKE) experiments, which should be responsible for the difference between the results of these two types of experiments. The present work demonstrates that TG technique is a useful alternative in the study of intermolecular dynamics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21173063 and 21203047)the Foundation of Heilongjiang Bayi Agricultural University,China(Grant No.XZR2014-16)+1 种基金NSAF(Grant No.U1330106)the Special Research Project of National Key Laboratory of Shock Wave and Detonation Physics,Institute of Fluid Physics,China Academy of Engineering Physics(Grant No.2012-S-07)
文摘The structural deformation induced by intense laser field of liquid nitrobenzene（NB） molecule,a typical molecule with restricting internal rotation,is tracked by time- and frequency-resolved coherent anti-Stokes.Raman spectroscopy（CARS） technique with an intense pump laser.The CARS spectra of liquid NB show that the NO2 torsional mode couples with the NO2 symmetric stretching mode,and the NB molecule undergoes ultrafast structural deformation with a relaxation time of 265 fs.The frequency of NO2 torsional mode in liquid NB（42 cm-1） at room temperature is found from the sum and difference combination bands involving the NO2 symmetric stretching mode and torsional mode in time- and frequency-resolved CARS spectra.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673211 and 21203047)the Foundation of Heilongjiang Bayi Agricultural University,China(Grant No.XZR2014-16)the Science Challenging Program of China(Grant No.JCKY2016212A501)
文摘The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.
