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Ultrafast dynamics of strong-field dissociative ionization of CH2Br2 probed by femtosecond soft x-ray transient absorption spectroscopy
| Content Provider | Semantic Scholar |
|---|---|
| Author | Loh, Zhi-Heng Leone, Stephen R. |
| Copyright Year | 2008 |
| Abstract | Ultrafast dynamics of strong-field dissociative ionization of CH 2 Br 2 probed by femtosecond soft x-ray transient absorption spectroscopy Zhi-Heng Loh and Stephen R. Leone ∗ Departments of Chemistry and Physics, University of California, Berkeley, CA 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 Abstract 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 2 Br 2 induced by 800 nm strong-field irradiation. At moderate peak intensities (2.0 × 10 14 W/cm 2 ), strong-field ionization is accompanied by ultrafast C–Br bond dissociation, producing both neutral Br ( 2 P 3/2 ) and Br* ( 2 P 1/2 ) atoms together with the CH 2 Br + 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 2 P 3/2 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 CH 2 Br 2+ 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 C 2 axis of the molecule along the polarization axis results in the production of the ion X 2 B 2 , B 2 B 1 and C 2 A 1 states, respectively. At higher peak intensities (6.2 × 10 14 W/cm 2 ), CH 2 Br 2+ undergoes sequential ionization to form the metastable CH 2 Br 22+ dication. These results demonstrate the potential of core-level probing with high-order harmonic transient absorption spectroscopy for studying ultrafast molecular dynamics. Corresponding author. Electronic mail: srl@berkeley.edu |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://digital.library.unt.edu/ark:/67531/metadc900154/m2/1/high_res_d/932710.pdf |
| Alternate Webpage(s) | https://cloudfront.escholarship.org/dist/prd/content/qt5tc0f7zm/qt5tc0f7zm.pdf |
| Alternate Webpage(s) | http://www.dtic.mil/dtic/tr/fulltext/u2/a513052.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
