Abstract

We have experimentally studied the survival probability of electronically excited molecules in collisions with solid surfaces. The molecular beam was produced by a pulsed nozzle. A fast ion gauge, a QMS, a pyroelectric foil (bolometer) and special light collecting optics were utilized as diagnostic tools. The QMS and the light detector could be rotated around the scattering center, thus allowing for angularly resolved measurements. Scattering from the foil directly revealed the free energy change involved in the scattering process. The molecules tested were Ni(CO)₄ and SO₂. XeCl laser (308 nm) excitation of Ni(CO)₄ yields the electronically excited fragment $\text{Ni}{\left(\text{CO}\right)}_3^{*}$ with unit efficiency. The radiative lifetime of $\text{Ni}{\left(\text{CO}\right)}_3^{*}$ is =17μs, that of SO₂ is > 55 μs for XeCl laser excitation. A long lifetime is essential for the experimental purpose because the excited portion of the beam must be monitored over a sufficiently long distance in front of and behind the scattering centre.

© 1987 Optical Society of America