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
Resonance enhanced two-photon ionization process of hydrogen atom via the resonant laser pulse is studied by Bohmian mechanics (BM) method. By analyzing the trajectories and energies of Bohmian particles (BPs), we fin...Resonance enhanced two-photon ionization process of hydrogen atom via the resonant laser pulse is studied by Bohmian mechanics (BM) method. By analyzing the trajectories and energies of Bohmian particles (BPs), we find that under the action of high frequency and low intensity multi-circle resonant laser pulses, the ionized BPs first absorb one photon completing the excitation, and then absorb another photon, completing the ionization after staying in the first excited state for a period of time. The analysis of work done by the forces shows that the electric field force and quantum force play a major role in the whole ionization process. At the excitation moment and in the excitation-ionization process, the effect of the quantum force is greater than that of the electric field force. Finally, we discuss the principle of work and energy for BPs, and find that the electric field force and quantum force are non-conservative forces whose work is equal to the increment of mechanical energy of the system. In addition, it is proved that the quantum potential energy actually comes from the kinetic energy of the system and the increment of kinetic energy is equal to that of the kinetic energy of the system.展开更多
Kr atoms were produced in their metastable states 4p55s [3/2]2 and 4p55s' [1/2]0 in a pulsed DC dis-charge in a beam,and subsequently excited to the even-parity autoionizing Rydberg states 4p5np' [3/2]1,2,[1/2...Kr atoms were produced in their metastable states 4p55s [3/2]2 and 4p55s' [1/2]0 in a pulsed DC dis-charge in a beam,and subsequently excited to the even-parity autoionizing Rydberg states 4p5np' [3/2]1,2,[1/2]1 and 4p5nf' [5/2]3 using single photon excitation.The excitation spectra of the even-parity autoionizing resonance series from the metastable Kr were obtained by recording the autoionized Kr+ ions with time-of-flight ion detection in the photon energy range of 29000-40000 cm1.A wealth of autoionizing resonances were newly observed,from which more precise and more systematic spec-troscopic data of the level energy and quantum defects were derived.展开更多
The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed...The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X2II(v=0,1)-A2(v' = 0,1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A2E+ and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.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 Jilin Province Science and Technology Development Plan Project-Excellent Youth Talents Fund Project,China(Grant No.20180520174JH)the National Natural Science Foundation of China(Grant Nos.1170414511904050,11774129,11747007,and 11534004).
文摘Resonance enhanced two-photon ionization process of hydrogen atom via the resonant laser pulse is studied by Bohmian mechanics (BM) method. By analyzing the trajectories and energies of Bohmian particles (BPs), we find that under the action of high frequency and low intensity multi-circle resonant laser pulses, the ionized BPs first absorb one photon completing the excitation, and then absorb another photon, completing the ionization after staying in the first excited state for a period of time. The analysis of work done by the forces shows that the electric field force and quantum force play a major role in the whole ionization process. At the excitation moment and in the excitation-ionization process, the effect of the quantum force is greater than that of the electric field force. Finally, we discuss the principle of work and energy for BPs, and find that the electric field force and quantum force are non-conservative forces whose work is equal to the increment of mechanical energy of the system. In addition, it is proved that the quantum potential energy actually comes from the kinetic energy of the system and the increment of kinetic energy is equal to that of the kinetic energy of the system.
基金Supported by the National Natural Science Foundation of China (Grant No. 20673107)the National Key Basic Research Special Foundation of China (Grant No. 2007CB815203)Chinese Academy of Sciences (Grant No. KJCX2-SW-H08)
文摘Kr atoms were produced in their metastable states 4p55s [3/2]2 and 4p55s' [1/2]0 in a pulsed DC dis-charge in a beam,and subsequently excited to the even-parity autoionizing Rydberg states 4p5np' [3/2]1,2,[1/2]1 and 4p5nf' [5/2]3 using single photon excitation.The excitation spectra of the even-parity autoionizing resonance series from the metastable Kr were obtained by recording the autoionized Kr+ ions with time-of-flight ion detection in the photon energy range of 29000-40000 cm1.A wealth of autoionizing resonances were newly observed,from which more precise and more systematic spec-troscopic data of the level energy and quantum defects were derived.
基金This work was supported by the Natural Science Foundation of Hebei Province under Grant No. 102090. L. Zhang's e-mail address is laser@mail.hbu.edu.cn.
文摘The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X2II(v=0,1)-A2(v' = 0,1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A2E+ and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.