Energy levels and Rotational Constants of the 4pσ B"^1Σ_u^+, 5pπ D"^1Π_u^- and 7pπ ^1Π_u^- states in H_2

Abstract

The absorption bands of H_2, B"-X(4,0), D"-X(2,0) and 7pπ -X(1,0), observed around about 803 A, are investigated by using the high resolution spectrum with the reciprocal dispersion 0.6cm-1. This wavelength region is corresponding to the first ionization energy of H_2. Its spectrum are fairly complicate, because of overlapping or masking with many Rydberg bands, of which belong to high members of npσ -X and npπ -X. In this work, the previous line assignments of these bands are examined in detail and are partly modified under the assumption of the perturbation between 7pπ -X(v=1) and 5pπ D"(v=1) bands. The previously observed photoionization peak near the R(0) line of B"-X(4,0) band, 124 354.8cm^<-1> has been 2.7cm^<-1> less to be assigned as the Q(1) line of 7pπ -X(1,0); the J=1 level, 124 473.3cm^<-1>, is below the autoionizing level, 124 476.0cm^<-1> (H_a^+, v=0, J=1). In absorption the R(0) line of B"-X is just superimposed by the Q(1) line of 7pπ -X(1,0) band. This problem is interpreted by consideration of the rotational perturbation. For persuasive interpretation of this localized perturbation, the reliable energy levels and electronic potential curves are essential. The R-K-R potentials require the precise molecular constants for the construction. The rotational and vibrational constants of the three states are evaluated and discussed in this work.