Observation of L uncoupling in the 5Δg1 Rydberg state of Na2

Abstract

The phenomenon of electronic orbital angular momentum L uncoupled from its internuclear axis has been observed in the sodium dimer using high-resolution cw optical-optical double-resonance spectroscopy. When L uncoupling occurs, the degeneracy of Lambda doubling is removed. In our experiment, the intermediate B (1)Pi(u) state of Na(2) is excited from the thermally populated ground X (1)Sigma(g) (+) state by a single-line Ar(+) laser. Then, a single-mode dye laser is used to probe the Rydberg states from the intermediate state. The signals are detected by monitoring the UV fluorescence from the triplet gerade states back to the a (3)Sigma(u) (+) state via collision energy transfer. Under our experimental resolution, the splitting of Lambda doubling in the 5 (1)Delta(g) state of Na(2) can be measured. A total of 136 rovibronic levels with ef parities have been assigned to the 5 (1)Delta(g) state. The Lambda-splitting constants deduced from these data are q(0)=0.376(90)x10(-4) cm(-1), q(v)=0.114(6)x10(-4) cm(-1), and mu=0.76(33)x10(-8) cm(-1). In general, the Lambda splitting of the Delta states is considerably smaller than that of the Pi states. However, the first-order splitting constants q(0) and q(v) reported here are larger than those in the B (1)Pi(u) state. This is due to the L uncoupling of the Rydberg states.

Molecular energies of the improved Rosen−Morse potential energy model

“…We also list the vibrational term values of the RKR potential. 41,43 Table 1 and Table 2 tell us that the vibrational levels determined by using the improved Rosen−Morse potential are in better agreement with the RKR values than those predicted by employing the Morse potential. By comparison of the present Table 1 with table 1 of Hu et al 44 , one can find that the vibrational energies for the 3 3 ⌺ g + state of the Cs 2 molecule calculated with the improved Rosen−Morse potential model are very close to those predicted by the improved deformed four-parameter exponential-type potential model.…”

“…Taking these experimental data as inputs, we yield the potential energy curve of the Na 2 5 1 ⌬ g state. The average absolute deviations of the improved Rosen−Morse potential and the Morse potential for the 5 1 ⌬ g state of Na 2 from the RKR potential reported by Chang et al 43 are 0.225% of D e and 0.792% of D e , respectively. This result shows that the improved Rosen−Morse potential is superior to the Morse potential in fitting the potential curve of the 5 1 ⌬ g state of Na 2 .…”

“…This result shows that the improved Rosen−Morse potential is superior to the Morse potential in fitting the potential curve of the 5 1 ⌬ g state of Na 2 . We present the RKR potential data points reported by Chang et al 43 for the potential energy curve of the 5 1 ⌬ g state of Na 2 in Fig. 2, which also contains the potential curves reproduced by the improved Rosen−Morse potential and the Morse potential.…”

Molecular energies of the improved Tietz potential energy model

“…This accuracy indicator has been used by Steele et al, 49 Zavitsas, 50 Gardner and von Szentpály, 51 and Hajigeorgiou 52 to evaluate the accuracy of some empirical potential energy functions for diatomic molecules. The average absolute deviations of the improved Tietz potential for the 5 1 ⌬ g state of Na 2 from the RKR potential reported by Chang et al 47 are 0.138% of D e and 0.792% of D e for the C 1 ⌸ u state of the Na 2 molecule from the RKR potential reported by Jastrzebski et al, 48 respectively. These average absolute deviations satisfy the Lippincott criterion, i.e., an average absolute deviation of less than 1% of the dissociation energy D e between predicted and observed energies at the RKR turning points of the latter.…”

“…Choosing these experimental data as inputs, we can determine the values of the parameters ␣ and q in the improved Tietz potential. We give the RKR potential data points reported by Chang et al 47 for the 5 1 ⌬ g state of Na 2 in Fig. 1, which also contains the potential curves reproduced by the improved Tietz potential.…”