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Simplified Cartesian Basis Model for Intrapolyad Emission Intensities in the Bent-to-Linear Electronic Transition of Acetylene

Journal Article · · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
DOI:https://doi.org/10.1021/jp5113608· OSTI ID:1638458
 [1];  [2];  [2];  [2]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Massachusetts Inst. of Technology, Cambridge, MA
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
+ Show Author Affiliations
The acetylene emission spectrum from the trans-bent electronically excited à state to the linear ground electronic $$\tilde{X}$$ state has attracted considerable attention because it grants Franck–Condon access to local bending vibrational levels of the $$\tilde{X}$$ state with large-amplitude motion along the acetylene ⇌ vinylidene isomerization coordinate. For emission from the ground vibrational level of the à state, there is a simplifying set of Franck–Condon propensity rules that gives rise to only one zero-order bright state per conserved vibrational polyad of the $$\tilde{X}$$ state. Unfortunately, when the upper level involves excitation in the highly admixed ungerade bending modes, ν4' and ν6', the simplifying Franck–Condon propensity rule breaks down—as long as the usual polar basis (with v and l quantum numbers) is used to describe the degenerate bending vibrations of the $$\tilde{X}$$ state—and the intrapolyad intensities result from complicated interference patterns between many zero-order bright states. In this article, we show that, when the degenerate bending levels are instead treated in the Cartesian two-dimensional harmonic oscillator basis (with vx and vy quantum numbers), the propensity for only one zero-order bright state (in the Cartesian basis) is restored, and the intrapolyad intensities are simple to model, as long as corrections are made for anharmonic interactions. As a result of trans ⇌ cis isomerization in the à state, intrapolyad emission patterns from overtones of ν4' and ν6' evolve as quanta of trans bend (ν3') are added, so the emission intensities are not only relevant to the ground-state acetylene ⇌ vinylidene isomerization, they are also a direct reporter of isomerization in the electronically excited state.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
FG02-87ER13671
OSTI ID:
1638458
Journal Information:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 5 Vol. 119; ISSN 1089-5639
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (1)

Fundamental mechanisms for molecular energy conversion and chemical reactions at surfaces journal August 2019

Figures / Tables (10)

TABLE I(p. 5)table TABLE I
TABLE II(p. 6)table TABLE II
FIG. 1(p. 8)figure FIG. 1
FIG. 2(p. 10)figure FIG. 2
TABLE III(p. 11)table TABLE III
TABLE IV(p. 11)table TABLE IV
FIG. 3(p. 12)figure FIG. 3
FIG. 4(p. 15)figure FIG. 4
FIG. 5(p. 18)figure FIG. 5
FIG. 6(p. 25)figure FIG. 6

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