Internal energy distribution of the NCO fragment from near-threshold photolysis of isocyanic acid, HNCO

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

DOI:https://doi.org/10.1021/jp952667r· OSTI ID:263222

Brown, S S; Berghout, H L; Crim, F F ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

We report the first measurement of the vibrational- and rotational-state distributions in the NCO fragment resulting from photolysis of HNCO. Recent studies have drawn conclusions about the photochemistry of HNCO and the vibrational distribution in the NCO fragment from observations of kinetic energy distribution of the H atom produced in this photolysis; however, there has been no direct observation of the NCO fragment itself. We use laser-induced fluorescence to detect the nascent NCO photoproducts and spectral simulations to extract vibrational-state populations. The rotational distributions, where we can measure them, show little excitation, and the vibrational energy preferentially appears in the bending mode. The vibrational-state distribution results directly from the excited-state geometry of the HNCO parent, in which the NCO group is bent. The dissociation proceeds from this bent NCO group to a linear NCO fragment, strongly exciting the bending mode. We find about 65% of the total energy in relative translation of the fragments, while 30% goes into vibration and 5% into rotation of NCO. 49 refs., 7 figs., 2 tabs.

• OSTI ID: 263222
• 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
EMISSION SPECTRA
ENERGY LEVELS
ENERGY SPECTRA
FLUORESCENCE
INORGANIC ACIDS
NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS