Ultrafast strong-field dissociative ionization dynamics of CH{sub 2}Br{sub 2} probed by femtosecond soft x-ray transient absorption spectroscopy
- Departments of Chemistry and Physics, University of California, Berkeley, California 94720 (United States) and Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)
Femtosecond time-resolved soft x-ray transient absorption spectroscopy based on a high-order harmonic generation source is used to investigate the dissociative ionization of CH{sub 2}Br{sub 2} induced by 800 nm strong-field irradiation. At moderate laser peak intensities (2.0x10{sup 14} W/cm{sup 2}), strong-field ionization is accompanied by ultrafast C-Br bond dissociation, producing both neutral Br ({sup 2}P{sub 3/2}) and Br* ({sup 2}P{sub 1/2}) atoms together with the CH{sub 2}Br{sup +} fragment ion. The measured rise times for Br and Br* are 130{+-}22 fs and 74{+-}10 fs, respectively. The atomic bromine quantum state distribution shows that the Br/Br* population ratio is 8.1{+-}3.8 and that the Br {sup 2}P{sub 3/2} state is not aligned. The observed product distribution and the time scales of the photofragment appearances suggest that multiple field-dressed potential energy surfaces are involved in the dissociative ionization process. At higher laser peak intensities (6.2x10{sup 14} W/cm{sup 2}), CH{sub 2}Br{sub 2}{sup +} undergoes sequential ionization to form the metastable CH{sub 2}Br{sub 2}{sup 2+} dication. These results demonstrate the potential of core-level probing with high-order harmonic transient absorption spectroscopy for studying ultrafast molecular dynamics.
- OSTI ID:
- 21104056
- Journal Information:
- Journal of Chemical Physics, Vol. 128, Issue 20; Other Information: DOI: 10.1063/1.2925268; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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