| Autor: |
Sándor P; Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA., Sissay A; Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA., Mauger F; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA., Gordon MW; Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA., Gorman TT; Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA., Scarborough TD; Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA., Gaarde MB; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA., Lopata K; Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA., Schafer KJ; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA., Jones RR; Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA. |
| Abstrakt: |
We study, experimentally and theoretically, the ionization probability of singly halogenated methane molecules, CH 3 Cl and CH 3 Br, in intense linearly polarized 800 nm laser pulses as a function of the angle between the molecular axis and the laser polarization. Experimentally, the molecules are exposed to two laser pulses with a relative time delay. The first, weaker pulse induces a nuclear rotational wave packet within the molecules, which are then ionized by the second, stronger pulse. The angle-dependent ionization yields are extracted from fits of the measured delay-dependent ionization signal to a superposition of moments of the rotational wave packet's angular distribution. Angle-dependent strong-field ionization (SFI) yields are also calculated using time-dependent density functional theory. Good agreement between measurements and theory is obtained. Interestingly, we find a marked difference between the angle-dependence of the ionization yields for these two halomethane species despite the similar structure of their highest occupied molecular orbitals. Calculations reveal that these differences are a result of multichannel (CH 3 Cl) vs single-channel (CH 3 Br) ionization and of increased hole localization on Br vs Cl. By adding calculations for CH 3 F, we can discern clear trends in the ionization dynamics with increasing halogen mass. These results are illustrative, as chemical functionalization and molecular alignment are likely to be important parameters for initiating and controlling charge migration dynamics via SFI. |
