The spectrum of H 2 : The bands ending on 2 p 1 II

Abstract

In a recent communication* a new system of bands in the molecular spectrum of hydrogen has been outlined. These bands were found to originate in known par-hydrogen levels having principal quantum numbers 3 and 4, and to go down to the 2 p 1 II or C level of Dieke and Hopfield. The present paper is an extension of the original, and also deals with some apparent anomalies in the rotational structure of the 2 p 1 II levels for the vibrational states corresponding to v ″ = 1, 2 and 3. These new bands were derived from the old bands to the 2 p 1 Σ or B state, together with the required infra-red interval between the 2 p 1 Σ and 2 p 1 II states, as determined from the existing ultra-violet data on transitions from these two states to the 1 s 1 Σ or A state of the molecule. Bands were found corresponding to transitions from 3 1 A, 3 1 C, 3 1 K, 3 1 O, 4 1 A, 4 1 B, 4 1 C, 4 1 E and 4 1 ϰ to 2 p 1 II. Since the A, B and C states with principal quantum numbers 3 and 4 are thought to be similar in nature, bands were expected for 3 1 B → 2 p 1 II transitions. These were not found in the original analysis, but in the present investigation, using Poetker’s* tables of infra-red lines together with those of Gale, Monk and Lee, these bands have been identified both for the 0′ → 0″ and 1′ → 1″ vibration transitions. The presence of these bands, together with the relative positions and corresponding behaviour of the branches of the A, B and C bands in the ( v, m ) diagram for both systems, are in strong support of the above assumption regarding the common nature of these states for both electronic levels. This point has already been discussed by Richardson in connection with the structure of their rotation levels.