Nonlinear Fourier-Transform Spectroscopy of D_2 Using High-Order Harmonic Radiation

摘要

High-order harmonic radiation is available to investigate ultrafast nonlinear optical phenomena, such as two-photon absorption process, in the vacuum and extreme ultraviolet wavelength region. We have determined the sequential two-photon dissociative ionization pathways of D_2 with the simultaneous irradiation of multiple order harmonics of a Ti:sapphire laser in the visible-vacuum ultraviolet region with the aid of both an interferometric autocorrelation measurement and a Fourier-transform spectroscopy. By analyzing the interferometric autocorrelation signals appearing in the measured momentum distribution of D ~+, we were able to decompose the measured momentum distribution into three momentum distribution images representing the three distinct dissociation pathways, which are sequentially two-photon excitation processes of D_2. D_2~+ is prepared in the electronic ground state of D_2~+, and then excited to the first excited state, leading to the dissociation into D ~+ and D.