Ultrafast Dynamics of Strong-Field Dissociative Ionization of CH2Br2 Probed by Femtosecond Soft X-Ray Transient Absorption Spectroscopy
CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
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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 CH2Br2 induced by 800 nm strong-field irradiation. At moderate peak intensities 2.0 x 1014 Wcm2, strong-field ionization is accompanied by ultrafast C-Br bond dissociation, producing both neutral Br 2P32 and Br 2P12 atoms together with the CH2Br fragment ion. The measured rise times for Br and Br are 130 x 22 fs and 74 x 10 fs, respectively. The atomic bromine quantum state distribution shows that the BrBr population ratio is 8.1 x 3.8 and that the Br 2P32 state is not aligned. The observed product distribution and the timescales of the photofragment appearances suggest that multiple field-dressed potential energy surfaces are involved in the dissociative ionization process. In addition, the transient absorption spectrum of CH2Br2 suggests that the alignment of the molecule relative to the polarization axis of the strong-field ionizing pulse determines the electronic symmetry of the resulting ion alignment of the Br-Br, H-H, and C2 axis of the molecule along the polarization axis results in the production of the ion.
- Inorganic Chemistry
- Atomic and Molecular Physics and Spectroscopy