Photoelectron spectroscopy of alkali metal tetramer anions: The anomalous spectrum of Li−4

Abstract

Microwave spectrum of alkali metal tetrahydroborate. III. Rotational transitions of LiBD4, NaBD4, and KBH4 in the ground vibrational states and molecular structures of MBH4 (M=Li, Na, and K) J. Chem. Phys. 102, 6961 (1995); 10.1063/1.469134Microwave spectrum of alkali metal tetrahydroborate. II. Rotational transitions in the ground and excited vibrational states and molecular structure of LiBH4We present the photoelectron spectrum of Li 4Ϫ . This spectrum displays a spectral pattern that is strikingly different from that of the other alkali tetramer anions. Using the photoelectron spectrum of Li 4Ϫ along with our previously measured photoelectron spectra of Na 4 Ϫ , K 4 Ϫ , and Rb 4 Ϫ plus other existing evidence, we find that Li 4Ϫ does not have a linear geometry, as do the tetramer anions of sodium, potassium, and rubidium. This observation indicates that for both anions and neutrals, lithium clusters appear to take on higher dimensional structures at smaller sizes than do sodium and probably other alkali clusters. By examining the clues found in its photoelectron spectrum, we then speculate as to what the structure of Li 4Ϫ may be and also summarize the present state of theoretical progress on this problem.

Density functional studies of LiN and LiN+ (N = 2–30) clusters: Structure, binding and charge distribution

“…1(a)] in agreement with literature [18]. The Li 6 þ cation has a shapeless symmetric than the neutral cluster-obtained by shifting one atom of the pentagon of Li 6 cluster to the opposite ''capping'' position. The lowest energy structure of Li 7 is, in consistence with the literature [17,25], a pentagonal bipyramid belonging to the D 5h point group.…”

“…Wu and Jones [22] have presented joint experimental/DFT study of neutral and hydrogenated clusters. There have also been a number of other studies such as those using Hartree-Fock theory [6,23] with or without electron correlation contributions, Moller Plesset (MP) level of theory, and Configuration interaction (CI) methods [24,25]. Except for a few [15, 18, 23(a)], the previous theoretical studies are limited to cluster size N 20.…”

“…This is particularly relevant while performing calculations within the framework of density functional theory (DFT) as the original approximations to DFT were based upon analytic expressions derived from exchange-only treatment of the free electron gas [1]. Though the structureless jellium model [2][3][4][5] accounts nicely for the relative stability of s-valence metal clusters, experiments [6,7] and calculations [8] suggest that Li clusters exhibit a complex interplay between geometry, electronic structure, and size. This cautions against the use of large approximations in the theoretical method employed to study Li clusters.…”

“…On the theoretical side, there is an immense array of studies on Li clusters involving both DFT as well as traditional quantum chemistry approaches. In the set of DFT studies, Zhao and coworkers [15] have studied medium-sized Li N clusters (N ¼ 20, 30, 40, 50); Fournier et al [16] have employed Kohn-Sham theory with local spin density (LSD) and gradient corrected functional (for N ¼ [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and used a Tabu search algorithm for structure optimization; Gardet et al [17] have proposed a structural growth pattern based on the pentagonal bipyramid and have studied the electronic properties of clusters with up to 20 atoms. Jose and Gadre [18] recently reported a molecular electrostatic potential (MESP) guided method for building Li N clusters (N ¼ 4-58) and optimizing small clusters by a DFT based method and larger ones via molecular tailoring approach.…”

Thermochemistry of Hydrocarbon Radicals

“…We primarily rely on electron affinity measurements obtained by a number of excellent groups doing negative ion photoelectron spectroscopy. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] We have also collaborated with Prof. W. Carl Lineberger at the University of Colorado, Boulder, on negative ion photoelectron spectra of systems of relevance to combustion kinetics. During a sabbatical visit by the PI in Boulder, we obtained spectra of the napthide anion, C 10 H 7 !…”