Photoionization and photodissociation of HCl(B [sup 1]Σ[sup +],J=0) near 236 and 239 nm using three-dimensional ion imaging (original) (raw)

The electronically excited states HCl * ͑E , Ј=0,JЈ=0͒ and HCl * ͑V , Ј=12,JЈ=0͒ have been prepared by two-photon resonant absorption of ground state HCl via Q͑0͒ transitions at 238.719 and at 236.000 nm, respectively. The consequent one-or two-photon excitation at the same wavelength results in the production of H + , Cl + , and HCl + ions. The speed distributions and anisotropy parameters ␤ for these ions have been determined by three-dimensional photofragment ion imaging based on a position-sensitive delay-line anode assembly. Several results are presented: first, we measured velocity ͑speed and angle͒ distributions for HCl + due to the electron recoil in the photoionization of HCl * . Such distributions give information on the photoionization process and on the vibrational distribution of HCl + after the laser pulse. Second, the measured ␤ parameters for Cl + and H + distributions give information on the symmetries of the upper states in the one-photon photoexcitation of HCl * . Third, the measured speed distributions for H + help to understand the mechanism of the photodissociation of HCl + ions.