# Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

## Abstract

We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}Σ{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup −1} for LiNa and by no more than 114 cm{sup −1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup −1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup −1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrationalmore »

- Authors:

- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0216 (United States)
- Department of Physics, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0220 (United States)

- Publication Date:

- OSTI Identifier:
- 22252843

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Chemical Physics

- Additional Journal Information:
- Journal Volume: 140; Journal Issue: 18; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 74 ATOMIC AND MOLECULAR PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; BLACKBODY RADIATION; DIMERS; DIPOLE MOMENTS; DISSOCIATION ENERGY; EINSTEIN COEFFICIENTS; ELECTRONEGATIVITY; ELECTRONS; EXCITATION; FUNCTIONS; POTENTIAL ENERGY; STIMULATED EMISSION; VIBRATIONAL STATES

### Citation Formats

```
Fedorov, Dmitry A., Varganov, Sergey A., E-mail: svarganov@unr.edu, and Derevianko, Andrei.
```*Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers*. United States: N. p., 2014.
Web. doi:10.1063/1.4875038.

```
Fedorov, Dmitry A., Varganov, Sergey A., E-mail: svarganov@unr.edu, & Derevianko, Andrei.
```*Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers*. United States. doi:10.1063/1.4875038.

```
Fedorov, Dmitry A., Varganov, Sergey A., E-mail: svarganov@unr.edu, and Derevianko, Andrei. Wed .
"Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers". United States. doi:10.1063/1.4875038.
```

```
@article{osti_22252843,
```

title = {Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers},

author = {Fedorov, Dmitry A. and Varganov, Sergey A., E-mail: svarganov@unr.edu and Derevianko, Andrei},

abstractNote = {We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}Σ{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup −1} for LiNa and by no more than 114 cm{sup −1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup −1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup −1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.},

doi = {10.1063/1.4875038},

journal = {Journal of Chemical Physics},

issn = {0021-9606},

number = 18,

volume = 140,

place = {United States},

year = {2014},

month = {5}

}