Ground and Excited States of Cali and Srli Ultracold Molecules
Ab initio study of ground and excited states of 6Li40Ca and 6Li88Sr molecules
Geetha Gopakumar1,2,a), Minori Abe1,2, Masahiko Hada1,2 and Masatoshi Kajita3
1Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji Tokyo, 192-0397, Japan,
2JST, CREST, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
3National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
a)Electronic mail: geetha@tmu.ac.jp.
ABSTRACT
We present quantum-chemical calculations for the ground and some low-lying excited states of isolated LiCa and LiSr molecules using multi-state complete active space second-order perturbation theory (MS–CASPT2). The potential energy curves (PECs) and their corresponding spectroscopic constants, obtained at the spin-free (SF) and spin-orbit (SO) levels, agree well with available experimental values. Our SO–MS-CASPT2 calculation at the atomic limit (R = 100 a.u.) with the largest basis set reproduces experimental atomic excitation energies within 3% for both LiCa and LiSr. In addition, permanent dipole moments (PDMs) and transition dipole moments (TDMs) at the SF level are also obtained. Rovibrational calculations of the ground and selected excited states, together with the spontaneous emission rates, demonstrate that the formation of ultracold LiCa and LiSr molecules in low-lying vibrational levels of the electronic ground state may be possible.
I. INTRODUCTION
Since the development of laser cooling, many research groups have directed their interest towards opening new fields of physics using ultracold (<10-3K) atoms/molecules to study cold collisions, quantum degeneracy, atom optics, and precise measurements. Recently, ultracold polar molecules have attracted attention in studies of anisotropic long-range dipole-dipole interactions1 in the ultracold regime. Although the application of laser cooling to molecules is difficult, several cooling methods, such as buffer gas cooling,2 Stark or
Geetha Gopakumar1,2,a), Minori Abe1,2, Masahiko Hada1,2 and Masatoshi Kajita3
1Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji Tokyo, 192-0397, Japan,
2JST, CREST, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
3National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
a)Electronic mail: geetha@tmu.ac.jp.
ABSTRACT
We present quantum-chemical calculations for the ground and some low-lying excited states of isolated LiCa and LiSr molecules using multi-state complete active space second-order perturbation theory (MS–CASPT2). The potential energy curves (PECs) and their corresponding spectroscopic constants, obtained at the spin-free (SF) and spin-orbit (SO) levels, agree well with available experimental values. Our SO–MS-CASPT2 calculation at the atomic limit (R = 100 a.u.) with the largest basis set reproduces experimental atomic excitation energies within 3% for both LiCa and LiSr. In addition, permanent dipole moments (PDMs) and transition dipole moments (TDMs) at the SF level are also obtained. Rovibrational calculations of the ground and selected excited states, together with the spontaneous emission rates, demonstrate that the formation of ultracold LiCa and LiSr molecules in low-lying vibrational levels of the electronic ground state may be possible.
I. INTRODUCTION
Since the development of laser cooling, many research groups have directed their interest towards opening new fields of physics using ultracold (<10-3K) atoms/molecules to study cold collisions, quantum degeneracy, atom optics, and precise measurements. Recently, ultracold polar molecules have attracted attention in studies of anisotropic long-range dipole-dipole interactions1 in the ultracold regime. Although the application of laser cooling to molecules is difficult, several cooling methods, such as buffer gas cooling,2 Stark or
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