Gwang-Hi Jeung

Interaction potentials of LiH, NaH, KH, RbH, and CsH

Quantum-mechanical calculations of the potential energy curves of the singlet and triplet states of LiH, NaH, KH, RbH, and CsH formed by the approach of ground state alkali–metal atoms and hydrogen atoms are presented. Precise values are determined for the coefficients of the van der Waals interaction and estimates are made of the contribution of the exchange interaction at large distances. Together with empirical data, they are used to assess and improve the accuracy of the ab initio potentials.

The D 1Σ+ state of 7LiH

The 7LiH D 1Σ+ excited electronic state has been observed for the first time by a pulsed optical–optical double resonance fluorescence depletion spectroscopic technique. Several rovibrational levels of the A 1Σ+ and B 1Π electronic states have been used as the intermediate states. Among 22 vibrational levels, 128 rovibrational levels have been observed. The spectral assignment is identified by the observed rotational structures and term values and by a comparison between the derived vibrational and rotational constants with the theoretical values. An ab initio adiabatic potential energy curve for the D 1Σ+ state and relevant D 1Σ+–A 1Σ+ and D 1Σ+–B 1Π transition moment functions are presented. An overall measure of three different aspects, the energetics, the spectral line shape, and the transition probability, strongly favors the argument that the vibronic approach is a better approach for characterizing the excited D 1Σ+ electronic state.

Singlet and triplet Σ+ excited states of NaH and KH: undulating potential energy curves

Abstract The 1 Σ + and 3 Σ + states of NaH dissociating into the 3s–5s states of Na and the 1 Σ + and 3 Σ + states of KH dissociating into the 4s–6p states of K are calculated using the effective core potential with the core polarization potential and the configuration interactions. Apart from ionic-neutral avoided crossings in cascade for the singlet states and neutral-neutral avoided crossings in both singlet and triplet states, all these states also show the undulating potential curves discovered recently: Phys. Rev. A 59 (1999) 1178–1186. The apparently complex potential curves are analyzed in this work.

Undulating potential curves of the Rydberg states of NaHe

Abstract The Rydberg states of alkali/rare-gas diatomic molecules show complex potential energy curves due to two effects: (1) avoided crossings between two close atomic configurations, and (2) undulations originating from the atomic orbital structures of the alkali Rydberg states. This work reports the potential energy curves for ten 2 Σ + states correlated to the atomic states from Na(3s) to Na(6s) obtained from accurate ab initio calculations. We give the spectroscopic constants and present a complete analysis for these potential curves.

Permanent and transition dipole moments in CaF and CaCl

Permanent and transition dipole moments have been calculated for various states of CaF and CaCl by using an effective one-electron variational eigenchannel R-matrix approach combined with generalized quantum defect theory. The ion core dipole moment has been evaluated ab initio. The calculations reproduce the existing measurements involving the lowest states of these compounds to within about 5%. The calculations yield for the first time electronic one-photon transition moments for excitation of the higher Rydberg series members, from the A 2Π, C 2Π or D 2Σ+ intermediate states. Permanent dipole moments for the higher Rydberg states have also been evaluated. It is found that the dipolar ion core causes an “internal” Stark effect to appear, such that certain series are characterized by strong positive dipole moments and other series are characterized by strong negative dipole moments.

Does the harpooning model apply to the alkali-dihydrogen reactions, A* + H2 → AH + H?

Abstract This work reports ab initio calculations for the alkali-dihydrogen reactions, A ∗ + H 2 → AH + H (with A=Li, Na, K), compared with the reaction, Li+F2→LiF+F. The electron transfers in those two types of reaction are proved to be entirely different. While the electron donation from the metal atom to the halogen molecule in the lithium–difluorine reaction occurs suddenly at a long intermolecular distance, the electron population is transferred progressively from the metal atom to the hydrogen molecule as the intermolecular distance decreases. We conclude that the harpooning model does not apply to the alkali-dihydrogen reactions.