Photodissociation studies of HNCO: heat of formation and product branching ratios

Journal Article · Thu Nov 06 04:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100281a025· OSTI ID:7005733

Spiglanin, T A; Perry, R A; Chandler, D W

The heat of formation (..delta..H/sub f/(298 K)) of HNCO is determined to be -24.9/sub -2.8//sup +0.7/ kcal/mol (based on ..delta..H/sub f/(NH) = 85.2 kcal/mol). This value is obtained by measuring the threshold for the production of NH(a/sup 1/..delta..) and by determining the energy contents of the NH fragment and the CO cofragment produced by photolysis of HNCO at wavelengths near the threshold. Saturated laser-induced fluorescence is used to determine the internal state distribution of NH(a/sup 1/..delta..), and multiphoton ionization is used to measure the internal state distribution of CO. An upper limit for the branching ratio of NCO/NH production from photodissociation of HNCO at 193 nm is determined from an analysis of kinetic experiments to be 0.10. To clarify the mechanism of photodissociation, HNCO fluorescence-excitation and NH(a/sup 1/..delta..) action spectra are also measured. They imply that two excited states of HNCO are present where only one had previously been considered.

• Research Organization: Sandia National Labs., Livermore, CA
• OSTI ID: 7005733
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:23; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONIC ACID DERIVATIVES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
ENERGY LEVELS
ENTHALPY
EXCITED STATES
EXPERIMENTAL DATA
FLUORESCENCE
FORMATION HEAT
INFORMATION
ISOCYANIC ACID
KINETICS
LASERS
LUMINESCENCE
NITROGEN COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
REACTION HEAT
REACTION KINETICS
THERMODYNAMIC PROPERTIES
THERMODYNAMICS