OBSERVATION OF THE SPLITTING OF THE VIBRONIC DEGENERACY UPON ASYMMETRIC DEUTERATION OF CYCLOPENTADIENYL RADICALS
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Date
1990
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Publisher
Ohio State University
Abstract
Rotationally resolved electronic spectra of asymmetrically deuterated cyclopentadienyl radicals $(Cp-d_{1} -d_{2} -d_{3}$ and $-d_{4}$) were recorded in a free jet expansion, Upon each deuteration, the origin band is blue-shifted by $50 cm^{-1}$ (from $C_{5}H_{5}'s\bar{A}\longleftrightarrow \tilde{X}$ origin at $29 572 cm^{-1}$), Asymmetric deuteration reduces the molecular symmetry from $D_{Sh}$ to $C_{2v}$, Correspondingly, the zero point level of the degenerate ground electronic state $(\tilde{X}^{2}E_{1})$ splits into two non-degenerate levels, $A_{2}$ and $B_{2}$. The order of the split levels are determined from the rotational band type. For $Cp-d_{1}$, it is $B_{2}$ above $A_{2}$, whereas for $Cp-d_{4}$, it is $A_{2}$ above $B_{2}$. In contrast to the symmetric $C_{5}H_{5}$ and $C_{5}D_{5}$, all the rotational constants of the asymmetric molecules could be simultaneously determined. The new information and its implications on the structure and Jahn-Teller effect will be discussed.
Description
Rotationally resolved electronic spectra of asymmetrically deuterated cyclopentadienyl radicals $(Cp-d_{1} -d_{2} -d_{3}$ and $-d_{4}$) were recorded in a free jet expansion, Upon each deuteration, the origin band is blue-shifted by $50 cm^{-1}$ (from $C_{5}H_{5}'s\bar{A}\longleftrightarrow \tilde{X}$ origin at $29 572 cm^{-1}$), Asymmetric deuteration reduces the molecular symmetry from $D_{Sh}$ to $C_{2v}$, Correspondingly, the zero point level of the degenerate ground electronic state $(\tilde{X}^{2}E_{1})$ splits into two non-degenerate levels, $A_{2}$ and $B_{2}$. The order of the split levels are determined from the rotational band type. For $Cp-d_{1}$, it is $B_{2}$ above $A_{2}$, whereas for $Cp-d_{4}$, it is $A_{2}$ above $B_{2}$. In contrast to the symmetric $C_{5}H_{5}$ and $C_{5}D_{5}$, all the rotational constants of the asymmetric molecules could be simultaneously determined. The new information and its implications on the structure and Jahn-Teller effect will be discussed.
Author Institution: Laser Spectroscopy Facility, Department of Chemistry
Author Institution: Laser Spectroscopy Facility, Department of Chemistry