TY - JOUR
T1 - Simplified cartesian basis model for intrapolyad emission intensities in the bent-to-linear electronic transition of acetylene
AU - Park, G. Barratt
AU - Steeves, Adam H.
AU - Baraban, Joshua H.
AU - Field, Robert W.
N1 - Publisher Copyright: © 2015 American Chemical Society.
PY - 2015/2/5
Y1 - 2015/2/5
N2 - The acetylene emission spectrum from the trans-bent electronically excited à state to the linear ground electronic X state has attracted considerable attention because it grants Franck-Condon access to local bending vibrational levels of the 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 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 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 vxand vyquantum 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.
AB - The acetylene emission spectrum from the trans-bent electronically excited à state to the linear ground electronic X state has attracted considerable attention because it grants Franck-Condon access to local bending vibrational levels of the 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 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 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 vxand vyquantum 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.
UR - http://www.scopus.com/inward/record.url?scp=84922423165&partnerID=8YFLogxK
U2 - https://doi.org/10.1021/jp5113608
DO - https://doi.org/10.1021/jp5113608
M3 - Article
SN - 1089-5639
VL - 119
SP - 857
EP - 865
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 5
ER -