Crossed-Beam Experiment on Rotational Population Distribution of OH (<i>A</i>²Σ⁺) Split from H₂O by Lyman Alpha Photon Impact

Abstract

The initial rotational population distribution of OH ( A 2 Σ + ) produced by Lyman Alpha photon impact on H 2 O has been measured by the crossed-beam technique. The light source employed is of the plasma-jet type, and it is highly monochromatic. The result obtained tells that the population is negligibly small in the lower rotational levels, and the overall distribution curve looks like an asymmetric peak with a narrow half-width situated at K '=17 to 22. Measurements have also been made in the target-gas method. However, these results are sensitive to the pressure of the target gas in the fluorescence cell, and they are all different more of less from the result obtained by the crossed-beam technique. Discussions about the discrepancy have led to secondary production of OH( A 2 Σ + ) due to long-lived species such as OH( X 2 Π), O( 1 D) and H( 2 S) because of their random motions in the target gas.