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Channel-resolved subcycle interferences of electron wave packets emitted from H_(2) in two-color laser fields

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High Power Laser Science and Engineering 2016年第4期4卷 1-7页

作者： Xinhua Xie Stefan Roither Daniil Kartashov Li Zhang Andrius Baltuska Markus Kitzler Photonics Institute Technische Universitat Wien Institute of Theoretical Chemistry University of Vienna

We report on the observation of subcycle interferences of electron wave packets released during strong field ionization of H_2 with cycle-shaped two-color laser fields. With a reaction microscope we measure three-dimensional momentum distributions of photoelectrons correlated with either H_2^+ or protons within different energy ranges generated by dissociation of H_2^+. We refer to these different types of photoelectrons as channels. Our results show that the subcycle interference structures of electron wave packets are very sensitive to the cycle shape of the two-color laser field. We explain this behavior by the dependence of the ionization time within an optical cycle on the shape of the laser field cycle. The subcycle interference structures can be further used to obtain insight into the subcycle dynamics of molecules during strong field interaction.

关键词： molecular dynamics strong field ionization wave packet interference

ionizations and fragmentations of benzene, methylbenzene, and chlorobenzene in strong IR and UV laser fields

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Chinese Physics B 2015年第11期24卷 212-216页

作者：张军峰吕航左万龙徐海峰金明星丁大军 Institute of Atomic and Molecular Physics Jilin University Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin University

ionizations and fragmentations of benzene, methylbenzene, and chlorobenzene are studied in linearly polarized 50-fs, 800-nm and 400-nm strong laser fields using a time-of-flight mass spectrometer. It is shown that at low laser intensity, the parent ions are dominant for any one of the molecules in an 800-nm strong laser field, while extensive fragmentation is observed in a 400-nm laser field, which can be understood by the resonant photon absorption of molecular cations. The ratio of the yield of the parent ion to the yield of the total ion for each molecule is measured as a function of laser intensity in a range from 1.0 × 1013 W/cm2 to 4.0 × 1014 W/cm2, in either the 800-nm or 400-nm laser field. The results show that the fragmentation of the aromatic molecules increases significantly as the laser intensity is increased. Possible mechanisms for fragmentation in strong laser fields are discussed. Finally, the saturation intensity of ionization of the titled molecules is also determined.

关键词： strong field ionization fragmentation benzene substitute benzene

Enhanced ionization of vibrational hot carbon disulfide molecules in strong femtosecond laser fields

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Chinese Physics B 2018年第6期27卷 257-261页

作者：左万龙吕航梁红静单石敏马日闫冰徐海峰 Institute of Atomic and Molecular Physics Jilin University Anhui Provincial Key Laboratory of Optoelectric Materials Science and Technology Anhui Normal University

By using a heated molecular beam in combination with a time-of-flight mass spectrometer, we experimentally study the ionization of vibrational-hot carbon disulfide（CS2） molecules irradiated by a linearly polarized 800-nm 50-fs strong laser field. The ion yields are measured in a laser intensity range of 7.0 × 10^（12） W/cm^2–1.5 × 10^（14） W/cm^2 at different molecular temperatures of up to 1400 K. Enhanced ionization yield is observed for vibrationally excited CS2 *** results show that the enhancement decreases as the laser intensity increases, and exhibits non-monotonical dependence on the molecular temperature. According to the calculated potential energy curves of the neutral and ionic electronic states of CS2, as well as the theoretical models of molecular strong-field ionization available in the literature, we discuss the mechanism of the enhanced ionization of vibrational-hot molecules. It is indicated that the enhanced ionization could be attributed to both the reduced ionization potential with vibrational excitation and the Frank–Condon factors between the neutral and ionic electronic states. Our study paves the way to understanding the effect of nuclear motion on the strongfield ionization of molecules, which would give a further insight into theoretical and experimental investigations on the interaction of polyatomic molecules with strong laser fields.

关键词： strong field ionization vibrational excited time-of-flight-mass spectrum