Dispersed fluorescence spectrum of acetylene from the A {sup 1}A{sub u} origin: Recognition of polyads and test of multiresonant effective Hamiltonian model for the X state

Journal Article · Thu May 09 04:00:00 EDT 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp953330s· OSTI ID:263220

Solina, S A.B.; O`Brien, J P; Field, R W ^[1]; Polik, W F ^[2]

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1. Massachusetts Inst. of Technology, Cambridge, MA (United States)
2. Hope College, Holland, MI (United States)

We have recorded a high-resolution dispersed fluorescence (DF) spectrum of the A {sup 1}A{sub u} YLD X {sup 1}{Sigma}{sup +}{sub g} transition of acetylene-h{sub 2}, utilizing the zero-point level of the A {sup 1}A{sub u} state. Here we present only the analysis of the vibrational levels of the X-state with E{sub vib} < 10000 cm{sup -1}. By comparing the observed and calculated spectral intensity patterns, we have estimated the previously undetermined pure bend vibrational constant, S{sup h(2)}{sub 45}, to be -11(2) cm{sup -1}. Unlike previously recorded DF spectra, this DF spectrum is uniquely suited for comparison with an effective Hamiltonian since (1) the Franck-Condon envelope facilitates observation of levels at lower E{sub vib} in the X-state, (2) the improved resolution is sufficient to observe intramolecular vibrational redistribution (IVR) at lower E{sub vib}, and (3) spectral features are no longer absent because of nodal patterns in the Franck-Condon envelope. Our comparison shows that our current effective Hamiltonian model, H{sup R}{sub eff}, can qualitatively describe the IVR pathways on the X-state for chromostates (zero-order bright states) which contain high excitation in the trans-bend (v{sub 4} <= 12). The failure of our model H{sup R}{sub eff} for chromostates which contain excitation in both the CC stretch (v{sub 2}) and the trans-bend (v{sub 4} > 8) may be attributed to a new stretch-bend or stretch-only resonance. 35 refs., 11 figs., 7 tabs.

• DOE Contract Number: FG02-87ER13671
• OSTI ID: 263220
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 19 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
ACETYLENE
ELECTRONIC STRUCTURE
EMISSION SPECTRA
ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
FLUORESCENCE
GROUND STATES
HAMILTONIANS
MATHEMATICAL MODELS
THEORETICAL DATA
VIBRATIONAL STATES