Raman spectroscopic investigation of small matrix-isolated lithium clusters

Abstract

The lithium clusters Li2, Li4, and Li8 have been isolated in argon matrices at 15 K and characterized by Raman spectroscopy. The vibrational frequencies are compared with configuration interaction (QCISD/6-311G* and CID/6-311G*) calculations and their assignment is supported by 6-lithium and 7-lithium isotopomers. The Li4 cluster possesses a rhombic structure (D2h) with calculated d(Li–Li)=272.6 and 306.4 pm, respectively. For octalithium, a hypertetrahedral structure (Td) is predicted in which each side of an inner tetrahedron with d(Li–Li)=292.5 pm is capped by lithium atoms with a distance of d(Li–Li)=304.2 pm. The octalithium cluster is an example of a matrix-isolated magic number cluster.

Orbitals in Inorganic Chemistry: Metal Rings and Clusters, Hydronitrogens, and Heterocyles

“…The Raman spectroscopy supported the rhombic structure for the Li 4 [44], Na 4 and K 4 clusters [45,46].…”

Ground‐state geometry and electronic structure of light atom clusters, especially H isotopes, Li, B, and C

“…For Li 8 , a hypertetrahedral structure (T d ) is predicted, which Kornath et al [5] take to be an example of a matrix-isolated magic number cluster.…”

“…The conclusion of Kornath et al [5] is then that the Li 4 cluster had a rhombic structure (D 2h ). For Li 8 , a hypertetrahedral structure (T d ) is predicted, which Kornath et al [5] take to be an example of a matrix-isolated magic number cluster.…”

“…Kornath et al note that most of these methods are difficult to correlate with cluster geometries-a major focus of the present article. However, from earlier experimental studies using Raman spectroscopy on small K and Na clusters in noble gas matrices [9,10], Kornath et al have shown that Raman spectroscopy, linked with quantum-chemical calculations, affords a reliable route to the determination of cluster geometries. Below our focus is solely on the lightest alkali, Li.…”

“…More recent theoretical work on doubly charged D clusters is also reported. Some attention is then given to results on small Li clusters, isolated in argon matrices by Kornath et al (2003), in relation to many-body theory. This is followed by a study of almost-spherical cages of B and of C atoms: both neutral and charged clusters again being referred to in the case of boron.…”