1. Quantum and quasi-classical effects in the strong field ionization and subsequent excitation of nitrogen molecules
- Author
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Liang Xu, Qi Lu, Vladimir T. Tikhonchuk, Bin Zhou, Runzhe Yang, Qingqing Liang, Feng He, Rostyslav Danylo, Aurélien Houard, André Mysyrowicz, Yi Liu, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Centre d'Etudes Lasers Intenses et Applications (CELIA), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), ELI Beamlines Center, Institute of Physics (ELI ), Key Laboratory for Laser Plasmas (MOE), CAS Center for Excellence in Ultra-Intense Laser Science, Interaction Laser-Matière (ILM), Laboratoire d'optique appliquée (LOA), École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), National Natural Science Foundation of China (12204308, 12034013, 11904232, 11925405, 91850203), Shanghai Municipal Education Commission (22ZR1444100), and Innovation Program of Shanghai Municipal EducationCommission (2017-01-07-00-07-E00007)
- Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Nonlinear optics ,Lasing effect ,Laser filamentation ,Atomic and Molecular Physics, and Optics ,Plasma physics - Abstract
The processes leading to the N2+ lasing are rather complex and even the population distribution after the pump laser excitation is unknown. In this paper, we study the population distribution at electronic and vibrational levels in N2+ driven by ultra-short laser pulse at the wavelengths of 800 nm and 400 nm by using the quantum-mechanical time-domain incoherent superposition model based on the time-dependent Schrödinger equation and the quasi-classical model assuming instantaneous ionization injection described by density matrix. It is shown that while both models provide qualitatively similar results, the quasi-classical instantaneous ionization injection model underestimates the population inversions corresponding to the optical transitions at 391 nm, 423 nm and 428 nm due to the assumption of quantum mixed states at the ionization time. A fast and accurate correction to this error is proposed. This work solidifies the theoretical models for population at vibrational states in N2+ and paves the way to uncover the mechanism of the N2+ lasing.
- Published
- 2022
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