Optical absorption probes of LixNa4−x (x=1,2): Geometry, substitution isomers, and composition-dependent electron delocalization

Abstract

Photodepletion spectra (415–763 nm, 10 Å effective resolution) were obtained for LiNa3 and Li2Na2 and compared to previous Na4 and Li4 measurements as well as to model calculations ranging from classical electrostatic to ab initio molecular orbital. Findings include (i) the assignment of planar rhombic singlet ground states for both molecules; (ii) in Li2Na2, the possibleobservation of predominantly one of three energetically close-lying planar rhombic or near rhombic substitution isomers; and (iii) in the sodium/lithium tetramer series, evidence for increasing localization of itinerant valence electrons with increasing cluster lithium content.

Structures and charge distributions of cationic and neutral Li X (X = Na and K)

“…Calculations [18][19][20] on the Li 2 Na 2 cluster indicates that the most stable neutral isomer is a rhombus ( 1 A g , D 2h ) configuration Fig. 1(i).…”

“…Dahlseid et al [19] and others [18,21] investigated several different neutral Li 3 Na isomers with ab initio and DFT methods. We support their predictions that the energetically most favorable isomer is the planar rhombus ( 1 A 1 , C 2v ) Fig.…”

“…However the laboratory spectroscopy has not yet been well explained due to the lack of the reliable information of their geometrical and electronic structures. Despite the geometrical arrangements of Li n Na m (n + m < 5) have been studied [18][19][20][21][22][23][24][25], their electronic charge distributions have not been reported. Deshpande et al [28,29] studies Li n Na and Na n Li (0 < n < 13) clusters with ab initio molecular dynamic method, however, the reliable geometrical structures and charge distributions of these clusters have not been given due to the limitation of the molecular dynamic methods.…”

“…In recent years a large number of binary clusters of lithium with some metallic or nonmetallic elements including sodium, aluminum, fluorine etc have been produced by laser vaporization of various lithium targets in high vacuum [18][19][20][21][22]26,27]. However the laboratory spectroscopy has not yet been well explained due to the lack of the reliable information of their geometrical and electronic structures.…”

“…2, 8, 18, 20, etc. Many theoretical calculations have been carried out for alkali metal clusters, however, most studies were focused on the pure alkali metal clusters [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], nevertheless much less is known for the mixed Li-Na or Li-K clusters [18][19][20][21][22][23][24][25].…”