In this work, we mainly investigate the NH3 molecular multiphoton ionization process by using the photoelectron velocity map imaging technique. Under the condition of femtosecond laser(wavelength at 800 nm), the photo...In this work, we mainly investigate the NH3 molecular multiphoton ionization process by using the photoelectron velocity map imaging technique. Under the condition of femtosecond laser(wavelength at 800 nm), the photoelectron images are detected. The channel switching and above-threshold ionization(ATI) effect are also confirmed. The kinetic energy spectrum(KES) and the photoelectron angular distributions(PADs) are obtained through the anti-Abel transformation from the original images, and then three ionization channels are confirmed successfully according to the Freeman resonance effect in a relatively low laser intensity region. In the excitation process, the intermediate resonance Rydberg states are C^1 A 1(6 + 2 photons process), B^1 E(6 + 2 photons process) and C^1 A 1(7 + 2 photons process), respectively. At the same time, we also find that the photoelectron angular distributions are independent of laser intensity. In addition, the electrons produced by different processes interfere with each other and they can produce a spider-like structure. We also find ac-Stark movement according to the Stark-shift-induced resonance effect when the laser intensity is relatively high.展开更多
We experimentally and numerically investigate CH_3I molecular alignment by using a femtosecond laser and a hexapole. The hexapole provides the single |111〉rotational state condition at 4.5-kV hexapole rod voltage. Ba...We experimentally and numerically investigate CH_3I molecular alignment by using a femtosecond laser and a hexapole. The hexapole provides the single |111〉rotational state condition at 4.5-kV hexapole rod voltage. Based on this single rotational state, an enhanced alignment degree of 0.73 is achieved. Our experimental results are in agreement with the simulation results. We experimentally obtain the ion velocity map images and show the influence of the initial rotational-state population. With the I+ion images and angular distributions at different pump-probe delay time, the alignment and anti-alignment phenomena are further demonstrated. The molecules will be under field-free conditions when the laser effect disappears completely at the full revival time. Our work shows that the quantum control and spatial control on CH_3I molecules can be realized and molecular coordinate frame can be obtained for further molecular experiment.展开更多
Coherent control of fragmentation of CH_3I using shaped femtosecond pulse train is investigated.The dissociation processes can be modulated by changing the separation of the shaped pulse train, and the yield of I^+und...Coherent control of fragmentation of CH_3I using shaped femtosecond pulse train is investigated.The dissociation processes can be modulated by changing the separation of the shaped pulse train, and the yield of I^+under the irradiation of the optimal pulse is significantly increased compared with that using the transform-limited pulse.We discuss the control mechanism of dissociation processes with coherent interference in time domain.A three-pulse control model is proposed to explain the counterintuitive experimental results.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
The ultrafast dissociation dynamics of NO2 molecules was investigated by femtosecond laser pump-probe mass spectra and ion images.The results show that the kinetic energy release of NO+ions has two components,0.05 eV ...The ultrafast dissociation dynamics of NO2 molecules was investigated by femtosecond laser pump-probe mass spectra and ion images.The results show that the kinetic energy release of NO+ions has two components,0.05 eV and 0.25 eV,and the possible dissociation channels have been assigned.The channel resolved transient measurement of NO^+provides a method to disentangle the contribution of ultrafast dissociation pathways,and the transient curves of NO^+ions at different kinetic energy release are fitted by a biexponential function.The fast component with a decay time of 0.25 ps is generated from the evolution of Rydberg states.The slow component is generated from two competitive channels,one of the channel is absorbing one 400nm photon to the excited state A^2B2,which has a decay time of 30.0ps,and the other slow channel is absorbing three 400nm photons to valence type Rydberg states which have a decay time less than 7.2ps.The channel and time resolved experiment present the potential of sorting out the complex ultrafast dissociation dynamics of molecules.展开更多
Nonadiabatic alignment by intense nonresonant the spatial direction of molecules： By solving the the degree of alignment of the molecules initially laser fields is a versatile technique to manipulate time-dependent S...Nonadiabatic alignment by intense nonresonant the spatial direction of molecules： By solving the the degree of alignment of the molecules initially laser fields is a versatile technique to manipulate time-dependent SchrSdinger equation numerically in different rotational state are calculated and the results show that the degree of alignment strongly depends on the initial rotational state. Thus, the present study indicates that, for obtaining a high degree of alignment for molecules, appropriate selection of molecular rotational states is necessary.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574116,11534004,10704028,and 11474123)
文摘In this work, we mainly investigate the NH3 molecular multiphoton ionization process by using the photoelectron velocity map imaging technique. Under the condition of femtosecond laser(wavelength at 800 nm), the photoelectron images are detected. The channel switching and above-threshold ionization(ATI) effect are also confirmed. The kinetic energy spectrum(KES) and the photoelectron angular distributions(PADs) are obtained through the anti-Abel transformation from the original images, and then three ionization channels are confirmed successfully according to the Freeman resonance effect in a relatively low laser intensity region. In the excitation process, the intermediate resonance Rydberg states are C^1 A 1(6 + 2 photons process), B^1 E(6 + 2 photons process) and C^1 A 1(7 + 2 photons process), respectively. At the same time, we also find that the photoelectron angular distributions are independent of laser intensity. In addition, the electrons produced by different processes interfere with each other and they can produce a spider-like structure. We also find ac-Stark movement according to the Stark-shift-induced resonance effect when the laser intensity is relatively high.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574116,11534004,10704028,and 11474123)the Natural Science Foundation of Jilin Province,China(Grant No.20170101154JC)
文摘We experimentally and numerically investigate CH_3I molecular alignment by using a femtosecond laser and a hexapole. The hexapole provides the single |111〉rotational state condition at 4.5-kV hexapole rod voltage. Based on this single rotational state, an enhanced alignment degree of 0.73 is achieved. Our experimental results are in agreement with the simulation results. We experimentally obtain the ion velocity map images and show the influence of the initial rotational-state population. With the I+ion images and angular distributions at different pump-probe delay time, the alignment and anti-alignment phenomena are further demonstrated. The molecules will be under field-free conditions when the laser effect disappears completely at the full revival time. Our work shows that the quantum control and spatial control on CH_3I molecules can be realized and molecular coordinate frame can be obtained for further molecular experiment.
基金Project supported by the National Natural Science Foundation of China(Grant No.11374124)
文摘Coherent control of fragmentation of CH_3I using shaped femtosecond pulse train is investigated.The dissociation processes can be modulated by changing the separation of the shaped pulse train, and the yield of I^+under the irradiation of the optimal pulse is significantly increased compared with that using the transform-limited pulse.We discuss the control mechanism of dissociation processes with coherent interference in time domain.A three-pulse control model is proposed to explain the counterintuitive experimental results.
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supported by the National Natural Science Foundation of China(No.11704148,No.11847039,No.11534004)
文摘The ultrafast dissociation dynamics of NO2 molecules was investigated by femtosecond laser pump-probe mass spectra and ion images.The results show that the kinetic energy release of NO+ions has two components,0.05 eV and 0.25 eV,and the possible dissociation channels have been assigned.The channel resolved transient measurement of NO^+provides a method to disentangle the contribution of ultrafast dissociation pathways,and the transient curves of NO^+ions at different kinetic energy release are fitted by a biexponential function.The fast component with a decay time of 0.25 ps is generated from the evolution of Rydberg states.The slow component is generated from two competitive channels,one of the channel is absorbing one 400nm photon to the excited state A^2B2,which has a decay time of 30.0ps,and the other slow channel is absorbing three 400nm photons to valence type Rydberg states which have a decay time less than 7.2ps.The channel and time resolved experiment present the potential of sorting out the complex ultrafast dissociation dynamics of molecules.
基金The work was supported by the National Basic Research Program of China （973 Program） under grant No. 2013CB922200 and the National Natural Science Foundation of China under grant Nos. 11034003 and 11127403.
文摘Nonadiabatic alignment by intense nonresonant the spatial direction of molecules： By solving the the degree of alignment of the molecules initially laser fields is a versatile technique to manipulate time-dependent SchrSdinger equation numerically in different rotational state are calculated and the results show that the degree of alignment strongly depends on the initial rotational state. Thus, the present study indicates that, for obtaining a high degree of alignment for molecules, appropriate selection of molecular rotational states is necessary.
