The autoionization branching ratios from Eu 4f76p1/26 d [J] autoionizing states to its 4f76s+(9So), 4f76s+(7So), and4f75d+(9Do) final ionic states are investigated with the combination of the three-step laser excitati...The autoionization branching ratios from Eu 4f76p1/26 d [J] autoionizing states to its 4f76s+(9So), 4f76s+(7So), and4f75d+(9Do) final ionic states are investigated with the combination of the three-step laser excitation and the velocity-map imaging technique. These different autoionizing states are excited via 4f76s6d8 DJ [J = 5/2, 7/2, and 9/2] intermediate states, respectively. The experimental photoelectron images are obtained, from which energy distributions of ejected electrons are achieved with the mathematical transformation. Furthermore, the energy dependence of the branching ratio is investigated within the autoionization resonance, by which population inversion is observed as an important characteristic.The J-dependence is also studied systematically. The validity of the well-known isolated core excitation technique used for obtaining the autoionization spectrum is also studied.展开更多
利用激光共振增强多光子电离技术,我们既可以观察中性物种激发态的振动结构也可以获得相应正离子的高分辨电子能谱.采用自行研制的双静电透镜系统对Xe原子在258.00 nm激光束下的三光子电离过程展开研究,优化得到飞行时间质谱的质量分辨...利用激光共振增强多光子电离技术,我们既可以观察中性物种激发态的振动结构也可以获得相应正离子的高分辨电子能谱.采用自行研制的双静电透镜系统对Xe原子在258.00 nm激光束下的三光子电离过程展开研究,优化得到飞行时间质谱的质量分辨率(m/Δm)达到1300,慢电子速度成像的电子能量分辨率(ΔE/E)为2.4%,阈值电子能量分辨优于1 me V.在该条件下,开展了分子的电子谱研究,研究了苯的激发电子态共振增强双光子电离光谱和振动态选择的苯正离子的慢电子速度成像谱,通过对谱线归属,获得了1B2u激发态的振动序列和苯正离子的振动能级结构信息.展开更多
The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 ...The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 + is employed as an intermediate state to initiate resonance enhanced two-photon excitation to high-lying dissociative states in the 4.0-5.0 eV energy region above the ground rovibronic state. Total kinetic energy release (TKER) and the twodimensional recoiling velocity distributions of fragmented 79Br+ ions are measured using the technique of DC-slice velocity map imaging. Branching ratios for individual state-resolved product channels are determined from the TKER spectra. The measured photofragment angular distributions indicate that the dissociation of 79Br2 + occurs in dissociative Ω=3/2 state via ΔΩ=0 parallel transition from the 14Σ-u;3=2 intermediate state. Due to the considerable spin-orbit coupling effects in the excited states of 79Br2 +, higher-lying dissociative quartet states are likely responsible for the observed photodissociation processes.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
We investigate the influence of the interaction volume on the energy resolution of a velocity map imaging spectrometer. The simulation results show that the axial interaction size has a significant influence on the re...We investigate the influence of the interaction volume on the energy resolution of a velocity map imaging spectrometer. The simulation results show that the axial interaction size has a significant influence on the resolution. This influence is increased for a higher kinetic energy. We further show that the radial interaction size has a minor influence on the energy resolution for the electron or ion with medium energy, but it is crucial for the resolution of the electron or ion With low kinetic energy. By tracing the flight trajectories we show how the electron or ion energy resolution is influenced by the interaction size.展开更多
The branching ratios of ions and the angular distributions of electrons ejected from the Eu 4f^76p_（1/2）nd auto-ionizing states are investigated with the velocity-map-imaging technique.To populate the above auto-ion...The branching ratios of ions and the angular distributions of electrons ejected from the Eu 4f^76p_（1/2）nd auto-ionizing states are investigated with the velocity-map-imaging technique.To populate the above auto-ionizing states,the relevant bound Rydberg states have to be detected first.Two new bound Rydberg states are identified in the region between41150 cm^（-1）and 44580 cm^（-1）,from which auto-ionization spectra of the Eu 4f^76p_（1/2）nd states are observed with isolated core excitation method.With all preparations above,the branching ratios from the above auto-ionizing states to different final ionic states and the angular distributions of electrons ejected from these processes are measured systematically.Energy dependence of branching ratios and anisotropy parameters within the auto-ionization spectra are carefully analyzed,followed by a qualitative interpretation.展开更多
基金This work is supported by the National Natural Science Foundation of China(No.22103075,No.21827804,and No.22173089)the National Key R&D Program of China(No.2021YFA0716801andNo.2017YFA0303502).
基金supported by the National Natural Science Foundation of China(Grant No.11174218)
文摘The autoionization branching ratios from Eu 4f76p1/26 d [J] autoionizing states to its 4f76s+(9So), 4f76s+(7So), and4f75d+(9Do) final ionic states are investigated with the combination of the three-step laser excitation and the velocity-map imaging technique. These different autoionizing states are excited via 4f76s6d8 DJ [J = 5/2, 7/2, and 9/2] intermediate states, respectively. The experimental photoelectron images are obtained, from which energy distributions of ejected electrons are achieved with the mathematical transformation. Furthermore, the energy dependence of the branching ratio is investigated within the autoionization resonance, by which population inversion is observed as an important characteristic.The J-dependence is also studied systematically. The validity of the well-known isolated core excitation technique used for obtaining the autoionization spectrum is also studied.
文摘利用激光共振增强多光子电离技术,我们既可以观察中性物种激发态的振动结构也可以获得相应正离子的高分辨电子能谱.采用自行研制的双静电透镜系统对Xe原子在258.00 nm激光束下的三光子电离过程展开研究,优化得到飞行时间质谱的质量分辨率(m/Δm)达到1300,慢电子速度成像的电子能量分辨率(ΔE/E)为2.4%,阈值电子能量分辨优于1 me V.在该条件下,开展了分子的电子谱研究,研究了苯的激发电子态共振增强双光子电离光谱和振动态选择的苯正离子的慢电子速度成像谱,通过对谱线归属,获得了1B2u激发态的振动序列和苯正离子的振动能级结构信息.
基金the National Natural Science Foundation of China(No.21773221 and No.21827804),the National Key R&D Program of China(2017YFA0303502),and Fundamental Research Funds for the Central Universities of China(WK2340000078).
文摘The [1+1] two-photon dissociation dynamics of mass-selected 79Br2 + has been studied in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ- u;3=2 state of 79Br2 + is employed as an intermediate state to initiate resonance enhanced two-photon excitation to high-lying dissociative states in the 4.0-5.0 eV energy region above the ground rovibronic state. Total kinetic energy release (TKER) and the twodimensional recoiling velocity distributions of fragmented 79Br+ ions are measured using the technique of DC-slice velocity map imaging. Branching ratios for individual state-resolved product channels are determined from the TKER spectra. The measured photofragment angular distributions indicate that the dissociation of 79Br2 + occurs in dissociative Ω=3/2 state via ΔΩ=0 parallel transition from the 14Σ-u;3=2 intermediate state. Due to the considerable spin-orbit coupling effects in the excited states of 79Br2 +, higher-lying dissociative quartet states are likely responsible for the observed photodissociation processes.
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 Nos.11234004 and 61275126)
文摘We investigate the influence of the interaction volume on the energy resolution of a velocity map imaging spectrometer. The simulation results show that the axial interaction size has a significant influence on the resolution. This influence is increased for a higher kinetic energy. We further show that the radial interaction size has a minor influence on the energy resolution for the electron or ion with medium energy, but it is crucial for the resolution of the electron or ion With low kinetic energy. By tracing the flight trajectories we show how the electron or ion energy resolution is influenced by the interaction size.
基金Supported by National Natural Science Foundation of China,11704178Natural Science Foundation of Hunan Province,2015JJ3104Research Foundation of Education Bureau of Hunan Province,15B204~~
基金supported by the National Natural Science Foundation of China(No.12374244,No.11974199)the National Key R&D Program of China(No.2018YFA0306504)Postdoctoral Fellowship Program of CPSF(No.GZC20231367)。
基金Project supported by the National Natural Science Foundation of China(Grant No.11174218)
文摘The branching ratios of ions and the angular distributions of electrons ejected from the Eu 4f^76p_（1/2）nd auto-ionizing states are investigated with the velocity-map-imaging technique.To populate the above auto-ionizing states,the relevant bound Rydberg states have to be detected first.Two new bound Rydberg states are identified in the region between41150 cm^（-1）and 44580 cm^（-1）,from which auto-ionization spectra of the Eu 4f^76p_（1/2）nd states are observed with isolated core excitation method.With all preparations above,the branching ratios from the above auto-ionizing states to different final ionic states and the angular distributions of electrons ejected from these processes are measured systematically.Energy dependence of branching ratios and anisotropy parameters within the auto-ionization spectra are carefully analyzed,followed by a qualitative interpretation.
