Photofragment vector correlations measured by transient absorption spectroscopy: CN fragments from ethyl thiocyanate photodissociation

Journal Article · Thu Oct 21 04:00:00 EDT 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100144a003· OSTI ID:5423661

Hall, G E; Wu, M ^[1]

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1. Brookhaven National Lab., Upton, NY (United States)

The correlated angular distribution of translational and rotational motion of photofragments is probed by Doppler-broadened transient absorption line shapes. The one-photon nature of the probe process reduces the complexity of the analysis, while maintaining sensitivity to five bipolar moments of the translational and rotational angular distributions. The 193-nm photodissociation of C[sub 2]H[sub 5]SCN illustrates the method, with CN products detected with a titanium:sapphire ring laser probing the A[sup 2][Phi]-[Chi][sup 2][Sigma][sup +] transition. The vector correlations in the high rotational states of CN indicate a direct dissociation following a transition of mixed symmetry at 193 nm: the recoil is preferentially but not exclusively parallel to a transition moment, and the perpendicular component is dominated by a rotation axis parallel to a C[sub 2]H[sub 5]SCN transition moment. The strong rotational excitation is generated by planar bending forces in a bent excited state. Lower rotational states are formed with a composite kinetic energy distribution, indicating an additional, slower, less highly polarized channel that partitions more energy into the unobserved C[sub 2]H[sub 5]S radical than does the direct channel. At 248 nm, a weaker absorption also generates CN photofragments with a preferentially parallel recoil, requiring a reassessment of the excited-state assignments in the alkyl thiocyanates. 42 refs., 7 figs., 7 tabs.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5423661
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:42; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ANTITHYROID DRUGS
CARBONIC ACID DERIVATIVES
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DOPPLER BROADENING
DRUGS
EXPERIMENTAL DATA
HORMONE ANTAGONISTS
INFORMATION
LASERS
LINE BROADENING
MATHEMATICAL MODELS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
SPECTROSCOPY
THEORETICAL DATA
THIOCYANATES