Structure and photoabsorption properties of cationic alkali dimers solvated in neon clusters

Abstract

We present a theoretical investigation of the structure and optical absorption of M(2)(+) alkali dimers (M=Li,Na,K) solvated in Ne(n) clusters for n=1 to a few tens Ne atoms. For all these alkali, the lowest-energy isomers are obtained by aggregation of the first Ne atoms at the extremity of the alkali molecule. This particular geometry, common to other M(2)(+)-rare gas clusters, is intimately related to the shape of the electronic density of the X (2)Σ(g)(+) ground state of the bare M(2)(+) molecules. The structure of the first solvation shell presents equilateral Ne(3) and capped pentagonal Ne(6) motifs, which are characteristic of pure rare gas clusters. The size and geometry of the complete solvation shell depend on the alkali and were obtained at n=22 with a D(4h) symmetry for Li and at n=27 with a D(5h) symmetry for Na. For K, our study suggests that the closure of the first solvation shell occurs well beyond n=36. We show that the atomic arrangement of these clusters has a profound influence on their optical absorption spectrum. In particular, the XΣ transition from the X (2)Σ(g)(+) ground state to the first excited (2)Σ(u)(+) state is strongly blueshifted in the Frank-Condon area.

Nonadiabatic molecular dynamics of photoexcited ${\rm Li}_2^+{\rm Ne}_n$ Li 2+ Ne n clusters

“…17 Since the surface hopping molecular dynamics is by nature a statistical method, we propagated a swarm of hundred trajectories for each system and each excited state we investigated in this paper. They are dominated by the clustering of the Ne atoms at the extremity of the Li + 2 molecule.…”

“…17 The modification of the PES by the surrounding Ne atoms reveals the strong confinement of the lowest energy states of the M + 2 molecules. 17 The modification of the PES by the surrounding Ne atoms reveals the strong confinement of the lowest energy states of the M + 2 molecules.…”

“…17 The case n = 1 is somewhat specific, mainly because the 1 2 + u and 1 2 u states are not well separated in the Frank-Condon area and it will not be discussed in this paper. 17 The case n = 1 is somewhat specific, mainly because the 1 2 + u and 1 2 u states are not well separated in the Frank-Condon area and it will not be discussed in this paper.…”

“…17 The case n = 1 is somewhat specific, mainly because the 1 2 + u and 1 2 u states are not well separated in the Frank-Condon area and it will not be discussed in this paper. 17 It is therefore worth presenting a state-by-state analysis of the dynamics for these three excited states. In view of the relatively large number of degrees of freedom and since the forces and nonadiabatic couplings can be efficiently computed, a method of choice is the surface hopping algorithm proposed by Tully, 18 which is based on classical dynamics.…”

Going beyond the frozen core approximation: Development of coordinate-dependent pseudopotentials and application to ${\rm Na}_2^+$ Na 2+

“…This is reminiscent of previous theoretical work done on Li + 2 , which also shows two distinct lobes for the valence orbital. 35 Panel (c) in Fig. 5 shows the bonding MO calculated from a UHF calculation using GAUSSIAN 03; clearly, the MQC calculation using our coordinate-dependent pseudopotential does an excellent job of reproducing the full quantum mechanically derived charge density.…”