Two-electron calculations for the intermediate Rydberg states of Na₂: molecular quantum defects

Abstract

Two-electron model potential calculations are presented for the 4-8'2; intermediate Rydberg states of Na,. The theoretical spectroscopic constants agree within 1% with the experimental results of Taylor er al. Two Rydberg series are identified; for one of them, the molecular quantum defect curve reveals a strong resonant character. Diabatic calculations show that the perturbation of this series is mainly due to an excitation of the Na: core into the two first excited states.

Diabatic representation for the excited states of the Na2 molecule: application to the associative ionization reaction between two excited sodium atoms

“…The subspaces P~ and Q~ are then deduced from pa and QA by replacing the configurations (% 3s) 2 and (a, 3s) z by XB and YB respectively. The present calculations differ from those reported in [12] because the QB subspace contains a larger number of configurations. The results are displayed in Table lb and in Fig.…”

“…(7), (8), (9) In (i0) n z is the principal quantum number (varying from 3 to 5 or 6 in our present calculations) and #Z(R) varies little from one value ofj to the next one. We have already discussed in [12] the identification of the 1Z+ series as "s" and "d" series. The two quantum defects #s and #d vary only of a few percent when j is changed, the ground state being not considered here and the first excited state differing more markedly from the rest of the series.…”

“…We have proposed in [12] an alternative construction for the 1Z~ diabatic states, in which we have first diagonalized the Hamiltonian in the subspace of the two configurations (% 3 s) 2 and (an 3 s) 2, hereby defining two eigenstates XB and Y~, XB being the lower one. The subspaces P~ and Q~ are then deduced from pa and QA by replacing the configurations (% 3s) 2 and (a, 3s) z by XB and YB respectively.…”

“…Adiabatic calculations have been performed, in the framework of a two-electron pseudo-potential [10,11] or model potential [12,13] approach, for the 2, H and A electronic excited states up to the 3p+3p dissociation limit. The comparison between the experimental and the theoretical spectroscopic constants [t3] provides a check of the accuracy of the calculations, which is estimated around 1%.…”

“…The comparison between the experimental and the theoretical spectroscopic constants [t3] provides a check of the accuracy of the calculations, which is estimated around 1%. Moreover, adiabatic molecular quantum defects can be deduced from the calculations [12] and compared with the results of a fit to experimental data [14]. However, the adiabatic picture is not well adapted to the treatment of the dynamical problem: it is more convenient to develop adiabatic picture so as to treat the molecular autoionization in the framework of the Multichannel Quantum Defect Theory (MQDT) first developed by Giusti [15] for the inverse process (dissociative recombination) and next applied to the H + H associative ionization [16].…”