VIBRATIONALLY RESOLVED NEGATIVE ION PHOTOELECTRON SPECTROSCOPIC STUDIES OF BARE TRANSITION METAL TRIMERS
Loading...
Date
1996
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
We report the 488 nm negative ion photoelectron spectra of the first row transition metal trimers $Cr_{3}$, $V_{3}$ and $V_{2}Ni$, which were prepared in a liquid nitrogen cooled flowing afterglow ion source. The photoelectron transitions to the lowest observed electronic states of $Cr_{3}$, $V_{3}$ and $V_{2}Ni$, which are assumed to be their ground states, each show two active vibrational modes with frequencies ($\pm$$15 cm^{-1}$) in the neutral clusters of 465 and $135 cm^{-1}$ ($Cr_{3}$), 470 and $205 cm^{-1}$ ($V_{3}$), and 415 and $250 cm^{-1}$ ($V_{2}Ni$). For the homonuclear trimers, these are assigned as the totally symmetric stretching and bending modes, respectively, of $C_{2}$, structures. In the mixed early-late transition metal cluster $V_{2}Ni$, the higher frequency mode may involve primarily V-V stretching and the lower one $Ni-V_{2}$ stretching and/or bending. For all three systems, a comparison of the observed stretching frequencies to those of $Cr_{2}$ ($452 cm^{-1}$) and ($530 cm^{-1}$), which have formal bond orders of 6 and 5, respectively, suggest that the triatomic clusters also contain multiple Cr-Cr or V-V bonds. A transition to an excited electronic state of $Cr_{3}$ lying 2850$\pm$20 $cm_{1}$ above its ground state is also observed, accompanied by a long vibrational progression in a (presumably bending) mode with a neutral molecule frequency of 170$\pm$15 $cm_{1}$ in this state. The electron affinities of $Cr_{3}$, $V_{3}$ and $V_{2}Ni$ are determined to be 1.389, 1.103 and 1.112 ($\pm$0.006) eV, respectively.
Description
Author Institution: Department of Chemistry, University of Minnesota