Homo- and heteronuclear alkali metal trimers formed on helium nanodroplets. Part II. Femtosecond spectroscopy and spectra assignments

Abstract

Homo-and heteronuclear alkali quartet trimers of the type K 3−n Rb n (n = 0, 1, 2, 3) formed on helium nanodroplets are probed by one-color femtosecond photoionization spectroscopy. The obtained frequencies are assigned to vibrations in different electronic states by comparison to high level ab initio calculations of the involved potentials including pronounced Jahn-Teller and spin-orbit couplings. Despite the fact that the resulting complex vibronic structure of the heavy alkali molecules complicates the comparison of experiment and theory we find good agreement for many of the observed lines for all species.

Desorption Dynamics of Rb2 Molecules Off the Surface of Helium Nanodroplets

“…21,22 Recently, the time-resolved study of rotational wave packet motion of molecules embedded in He droplets revealed that molecular rotation is significantly slowed down compared to isolated molecules and that rotational recurrences were completely absent. 23 This is in contrast to our previous observation of long-lasting coherent vibrational motion of Na 2 , K 2 , Rb 2 , and Rb 3 molecules formed on the surface of He droplets [24][25][26][27][28] which we interpreted in terms of weak system-bath couplings. 27,29 However, no clear signature of the desorption process of Rb 2 off the droplet surface was seen so that some uncertainty has remained with regard to the location of the molecule after excitationon the droplet surface or in the vacuum.…”

“…This work extends previous experimental studies of the desorption process of alkali (Ak) metal atoms on the one hand, 3,[12][13][14]18,30,31 and on of the vibrational wavepacket dynamics of Ak dimers and trimers formed on He droplets on the other. [24][25][26][27][28] Ak metals are particularly well-suited for these studies due to their location in shallow dimple states at the droplet surface. [32][33][34] Upon electronic excitation, Ak metal atoms and molecules tend to desorb off the He droplet as a consequence of repulsive interaction caused by the overlap of their extended valence orbitals with the surrounding He.…”

Potential energy surfaces of the low-lying electronic states of the Li + LiCs system

“…The investigations are carried out in the three main streams: the electronic structure properties, the dissociation or fragmentation processes and the association processes. The very extensive experimental and theoretical studies on the heteronuclear and homonuclear alkali trimers were given by the group of Ernst [1,2,3,4,5], where alkali quartet trimers formed on helium nanodroplets are probed by one-color femtosecond photoionization spectroscopy. The observation of predissociation in the mixed alkali trimer clusters was reported by the experimental group of Wöste [6].…”

Photoionisaton of pure and doped helium nanodroplets

“…Nevertheless, all prominent frequency components measured for K 3 and Rb 3 could be assigned to the normal vibrational modes of the ground and first excited quartet states by comparing with high-level ab initio calculations carried out by A. Hauser in Graz (Fig. 8 (b)) [151].…”