Highly vibrationally excited {sup 12}C{sub 2}H{sub 2} in the {ital {tilde X}}{sup 1}{summation}{sup +}{sub {ital g}} state: Complementarity of absorption and dispersed fluorescence spectra

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.472995· OSTI ID:399772

Temsamani, M A; Herman, M ^[1]; Solina, S A; OBrien, J P; Field, R W ^[2]

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1. Laboratoire de Chimie Physique Moleculaire CP160/09, Universite libre de Bruxelles, Roosevelt Ave, 50, B-1050 (Belgium)
2. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

Direct absorption and dispersed fluorescence (DF) spectra sample the {sup 12}C{sub 2}H{sub 2} {ital {tilde X}}{sup 1}{Sigma}{sup +}{sub {ital g}} potential energy surface via profoundly different zero-order bright states. Despite the complementary nature of the data sets, a polyad model based on the approximate quantum numbers, {ital N}{sub {ital s}}={ital v}{sub 1}+{ital v}{sub 2}+{ital v}{sub 3}, {ital N}{sub {ital r}}=5{ital v}{sub 1}+3{ital v}{sub 2}+5{ital v}{sub 3}+{ital v}{sub 4}+{ital v}{sub 5}, {ital l}={ital l}{sub 4}+{ital l}{sub 5}, accounts for the energies ({plus_minus}0.35 cm{sup {minus}1}) and relative intensities for all transitions into pure bending levels ({ital N}{sub {ital s}}=0) at {ital E}{sub vib}{le}12000 cm{sup {minus}1} and {ital N}{sub {ital r}}{le}15, {ital l}=0 and 2. The parameters that define this model are obtained by fitting 41 pure bending levels, of which 9 are {ital J}=0 energies derived from components of the [{ital N}{sub {ital s}}=0, {ital N}{sub {ital r}}=8, 10, 12, {ital l}=0, {ital g}] polyads observed in the DF spectrum. This polyad model provides a basis for extrapolating a description of otherwise indescribably complex spectra and dynamics to the {ital E}{sub vib}{approx_equal}16000 cm{sup {minus}1} region of the barrier to acetylene {leftrightarrow} vinylidene isomerization, and could therefore provide a basis for detecting the pattern-breaking signature of the onset of isomerization. {copyright} {ital 1996 American Institute of Physics.}

• DOE Contract Number: FG02-87ER13671
• OSTI ID: 399772
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 24 Vol. 105; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ABSORPTION SPECTROSCOPY
ACETYLENE
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
FLUORESCENCE SPECTROSCOPY
INTERMOLECULAR FORCES
ISOMERIZATION
POTENTIAL ENERGY SURFACES
VIBRATIONAL STATES
VINYLIDENE RADICALS