Reactive collision with excited states in a crossed beam experiment: O(1D)+H2(v)→OH(A 2Σ+)+H

At least for its most probable mechanisms, the reaction O(1D)+H2(X 1∑+g) →OH(A 2∑+)+H(1 2S) entirely takes place, from reagents to products, on electronically excited-state channels. Due to its endoergicity and to probable energy barriers (E*≊2.8 eV) encountered on these channels, the reaction can be produced in a crossed beam experiment only if the hydrogen molecule is excited on high vibrational levels (v≥5 or v≥7, according to the presence or the absence of energy barriers). This is obtained here by low-energy electron bombardment of the H2 molecular beam. The reaction is observed through the spontaneous fluorescence of the product OH. The measured spectrum corresponding to the 0–0 band of the A 2∑+→X 2Π transition is compared to simulated spectra, as obtained with a simple statistical model and with fitted rotational distribution for OH(A 2∑+,v=0): a broad rotational distribution and a strongly nonstatistical effect on the spin doublet populations are observed.