High-Resolution Study of theÃ2A′ → X2A″ Transition of HO2: Analysis of the 000–000 Band

A Theoretical Investigation of the Renner Interactions and Magnetic Dipole Transitions in the ÖX̃ Electronic Band System of HO2

“…Presumably, the X state energy levels in the vicinity of the à vibrational ground state are not calculated with sufficient accuracy for the effects of the significant interactions to be accurately described. This suspicion is confirmed by the fact that even though in the analysis of the à (0, 0, 0) 3 X (0, 0, 0) band Fink and Ramsay (9) showed that there must be a perturbing X vibronic state in the immediate vicinity of the à vibrational ground state at 7030 cm Ϫ1 , the X vibronic states that we calculate closest to this position are the X (v 1 , v 2 , v 3 ) ϭ X (1, 1, 2) state at 6920 cm Table 4 we also list the 20 strongest magnetic dipole lines in this band with their calculated positions (increased by 15 cm Ϫ1 ), linestrengths, and intensities for T ϭ 350 K.…”

“…The molecular symmetry group of HO 2 is the group C s (M) given in Table A-2 of (13), and using this group à (0, 0, 0) 3 X (0, 0, 0 (9). e Observed relative intensity (9).…”

“…The assignments were aided by the transition wavenumbers for ⌬N ⌬J transitions with low N, calculated on our request by Drs. Fink and Ramsay from a standard Watsonian model with the parameters in Table 4 of (9).…”

“…Thus we modeled the initial population distribution as a Boltzmann distribution in the rovibronic levels that are predominantly à 2 AЈ state levels, and we assumed that the other rovibronic levels were unpopulated. We took the Boltzmann distribution temperature in the à 2 AЈ state levels to be 350 K, based on Fink and Ramsay's analysis (9). Transitions originating from upper state levels that are more than 10 000 cm Ϫ1 above the X 2 AЉ state zero point level were discarded.…”

“…The à -X electronic band system of HO 2 in the gas phase was studied in 1974, both in emission and in absorption (6,7), and it was realized that forbidden ⌬K a ϭ 0 transitions are present; Tuckett et al (8) suggested that these transitions result from the Renner interaction. Fink and Ramsay (9), in a recent reinvestigation of the à (0, 0, 0) 3 X (0, 0, 0) band at high resolution, found that many of the forbidden transitions must be interpreted as magnetic dipole transitions since they connect rovibronic states of the same parity. Magnetic dipole transitions are usually too weak to be observed among electric dipole transitions, but HO 2 is a favorable case since the electric dipole transition moment for the electronic transition is very small.…”