Infrared laser spectroscopy of H2 and D2 Rydberg states. II. Diode laser spectra and assignment of 5g–4f, 6h–5g, and 8i–6h systems

Abstract

Infrared diode laser absorption spectra of portions of the 5g–4f, 6h–5g, and 8i–6h Rydberg bands of H2 and D2 have been measured at Doppler limited resolution in low pressure A. C. discharges. The spectra, arising from L uncoupled states of H2 and D2, are assigned using an ab initio polarization model supported by intensity calculations. Details of the different implementations of this polarization model are given in the preceding paper. The most useful was the single channel vibrationally extended (1)/(2) V6 model which became progressively better at higher n (and L). Results of multichannel calculations for a selected set of transitions are also reported.

Fine structure of the H2 5g–4f inter-Rydberg transition revealed by difference frequency laser spectroscopy

“…The present experiment easily resolves the singlet and triplet splitting observed previously; 10,12 for example, the singlet and triplet lines of R 2 (5)v ϩ ϭ1 are shown in Fig. 1.…”

“…1. Such splitting decreases rapidly with l. Singlet-triplet splitting was not observed in the diode laser work 12 on the 6h -5g system of H 2 , and since this work obtained similar resolution to that of the present experiment it is obvious that the observed splitting is essentially due to the 4 f state. The presently available ab initio calculations, however, do not include the electron exchange effects necessary to calculate such a splitting.…”

“…A feature of the spectrum not previously observed 10,12 is the presence of weak satellites accompanying the singlettriplet pairs. Figure 3 illustrates the fine structure of the R 3 (2)v ϩ ϭ0 transition.…”

“…The difference frequency laser system provides greater sensitivity and resolution than the FTIR experiment, and greater coverage was obtained in this study than that obtained in the diode laser investigations; 12 consequently, a large number of lines not seen in previous studies were observed. These included many weak Q branch lines and a few even weaker P branch lines whereas in the original studies only R-branch lines had been observed.…”

“…Since then, various transitions have been observed involving intercombinations of the high-l Rydberg states 3d, 4d, 4f , 5f , 5g, 6g, 6h, 7h, 7i, and 8i using Fouriertransform infrared ͑FTIR͒ spectroscopy 9,10 and diode laser spectroscopy. 3,11,12 Also, microwave spectroscopy ͑see, for example, Sturrus, Hessels, Arcuni, Lundeeen, 13 and refer-ences therein͒ has been used to study inter-Rydberg transitions with nϾ9 to very high precision. In the absence of autoionization or predissociation, these high-l states have lifetimes which are long enough to allow very precise determination of their energies.…”