M + Ng potential energy curves including spin-orbit coupling for M = K, Rb, Cs and Ng = He, Ne, Ar

Abstract

The X(2)Σ(1/2)(+), A(2)Π(1∕2), A(2)Π(3∕2), and B(2)Σ(1/2)(+) potential energy curves and associated dipole matrix elements are computed for M + Ng at the spin-orbit multi-reference configuration interaction level, where M = K, Rb, Cs and Ng = He, Ne, Ar. Dissociation energies and equilibrium positions for all minima are identified and corresponding vibrational energy levels are computed. Difference potentials are used together with the quasistatic approximation to estimate the position of satellite peaks of collisionally broadened D2 lines. The comparison of potential energy curves for different alkali atom and noble gas atom combinations is facilitated by using the same level of theory for all nine M + Ng pairs.

Potential energy curves for the interaction of Ag($\mathbf {5}{\bm s}$5s) and Ag($\mathbf {5}{\bm p}$5p) with noble gas atoms

“…This behavior was already observed in alkali-noble gas PECs. 45 The 2 1/2 state of Ag−He presents two minima separated by a barrier peaking at R = 6.95a 0 with a maximum energy of 91.2 cm −1 . The first minimum is located at R = 4.41a 0 , which is almost the same value as in the 2 3/2 state.…”

“…This behavior was already observed in other systems, e.g., involving alkali metals-noble gas complexes. 44,45 The PEC of the A 2 state was previously investigated for Ag−He. 18,23,46 Our results agree well with the calculations of Brahms et al, 18 which were also performed using the CCSD(T) method.…”

A CASPT2 study of the spectral shift of the resonance emission lines of Rb and Cs embedded in liquid He

“…One appears at a smaller distance compared to that of the ground state minimum, corresponding to 3.12 Å for Rb-He and 3.44 Å for Cs-He [29]. A cluster with this radius appears to be inappropriate.…”

“…As a first alternative, one can utilize the CASPT2 calculation to obtain the potential for the first excited state. However the calculations showed a discrepancy in the potential curves for distances greater than 8 Å. Consequently, as an alternative, we used the potential energy curve of Blank et al [29], to obtain the size of the cluster. The alkali-He pair potential of the ground and first excited states have been calculated using spin-orbit coupled multi-reference singles and doubles configuration interaction (SOCI) [39,40].…”

“…One major difficulty is to assign correctly the size of the active space [28], balancing the emission in the gas phase and in the model cluster due to surrounding He atoms. The pair potential, existing in the literature for Rb-He and Cs-He in their ground and excited states [29][30][31][32][33], have been utilized here.…”