A quantum defect analysis of heavy Rydberg behaviour in the BΣu+1

Continuity of heavy Rydberg behaviour in the ungerade ion-pair states of H 2

“…Here, H 12 $ 20 cm À1 . (This value is quite small when compared to the interaction matrix element of the avoided crossing of the B 1 R þ u curve and the B 00 B 1 R þ u curve (H 12 $ 3000 cm À1 ) at lower energy and smaller internuclear separation studied previously [12]). The weak interaction between the four states that meet at the (1s; 3l) dissociation limit can also be gauged by the minimal displacement in quantum defect of the highest vibrational level (v 0 ¼ 59) of the B 00 B 1 R þ u state located just 15 cm À1 below the crossing.…”

“…Specifically, the model potential consists of the doubly-excited state at short internuclear spacing to form the inner repulsive wall, the B state at mid-range to form the well, and the H + H À ion-pair potential at long-range to form the attractive outer wall. The consecutive vibrational counting does not include the v 0 ¼ 36 level, due to its strong inner-well character [12]. The calculated quantum defects of the above-threshold levels using the vibrational assignments made in this way are listed in Table 1 and are plotted in Fig.…”

“…We first consider HR behaviour in the B 00 B 1 R þ u state below the ð1s; 3lÞ threshold and extend the previous quantum defect analysis by Lawley and Donovan [12] to include the lower, below-barrier, outer-well vibrational levels, v 0 ¼ 0-16, predicted by Wolniewicz et al [15] Note that v 0 corresponds to outer-well vibrational numbering exclusive of the inner-well vibrational levels. These theoretical predictions agree with experiment, where available [19,20], to within $ 0:1 cm À1 .…”

“…2. The first region, E b % 8500-17; 000 cm À1 , corresponds to the vibrational levels of the outer-well B 1 R þ u state below the double-well barrier, and its linearity is a characteristic of HR behaviour seen in a wide range of other ion-pair states [1][2][3][4]12]. The second region, E b % 6000-8500 cm À1 , includes levels of the B 00 B 1 R þ u state above the double-well barrier, but below the (1s; 3l) threshold.…”

“…Measured energies of vibrational levels below the (1s; 2l) dissociation threshold belonging to the lowest ungerade excited state, the B 1 R þ u state, were recently treated with the HR model, and HR behaviour was found to be continuous from v 0 ¼ 0 up to nearly the (1s; 2l) dissociation limit [12]. HR behaviour was also found in a new analysis of the vibrational levels of the higher energy double-well B 00 B 1 R þ u state up to the ð1s; 3lÞ dissociation limit [12].…”