Water molecules in ultrashort intense laser fields

摘要

Ionization and excitation of water molecules in intense laser pulses are studied theoretically by solving the three-dimensional time-dependent electronic Schr?dinger equation within the single-active-electron approximation. The possibility to image orbital densities by measurement of the orientation-dependent ionization of H_2O in few-cycle, 800 nm linear-polarized laser pulses is investigated. While the highest-occupied molecular orbital 1b_1 is found to dominate the overall ionization behavior, contributions from the energetically lower lying 3a_1 orbital dominate the ionization yield in the nodal plane of the 1b_1 orbital. The ratio of the ionization yields of the two orbitals depends on the intensity. Furthermore, even for laser pulses as long as 8 cycles the orientation-dependent ion yield depends on the carrier-envelope phase. In the interpretation of the orientation-dependent ionization as an imaging tool these effects have to be considered.