Vibration rotation interaction in OH and the transition moment

Abstract

A re-examination of the intensity distribution in the A 2 ∑ - X 2 π ultraviolet bands of OH leads to a vibrational transition moment R ev (r) = exp { — (5·97 ± 0·12) r }, where r is the internuclear distance in Ångströms. It is shown that this value for the transition moment will not explain the variation of intensity with rotational quantum number. The interaction of rotation and electronic motion leads to a second, rotational, transition moment. This term is related to the centrifugal distortion of the molecule, and for the (0, 0) band is given by R eJ (r) = exp { + (3·60 ± 1·0) x 10 -4 J ( J + 1}. Within the (0, 0) band the combination of these two moments is equivalent to a single function R e (r) = exp { — (2·67 ± 0·9) r }. In consequence (0, 0) band vibration-rotation interaction and temperature corrections remain as given by Learner (1962). The relative J dependent vibra­tional transition probabilities for the rest of the system are corrected. The effect of the rotational transition moment on the measurement of rotational temperature is discussed for both OH and other diatoms.