TY - JOUR
T1 - Photodissociation of RNCS and RSCN (R = H, CH3, C 2H5) at 248 and 193 nm
T2 - CN product energy distributions
AU - Northrup, F. J.
AU - Sears, Trevor J.
PY - 1990
Y1 - 1990
N2 - Photodissociation of the molecules RNCS and RSCN (R = H, CH3, and C2H5) was investigated at 248 and 193 nm and the internal energy distributions in the CN resulting from the RS + CN fragmentation channel were probed by laser induced fluorescence. These CN distributions were identical for formation from the isomer pairs in agreement with an excited state isomerization postulated earlier. At 248 nm, all precursors lead to nearly thermal CN rotational distributions with rotational temperatures of approximately 1100 K in v = 0 and 800 K in v = 1. The vibrational distributions could not be characterized by the same temperatures. At 193 nm, contributions from two apparently different dissociation channels were observed. The CN rotational populations showed a narrow, strongly peaked distribution lying on a broad, approximately statistical distribution. For HNCS, this peak occurs near N = 10 suggesting dissociation from an excited state with a linear NCS skeleton. For the alkyl precursors, the peak occurs at very high rotational quantum number (N = 70) indicating an excited state with a bent NCS framework. Vibrational distributions with population out to v = 6 were observed. In all cases, the apparent statistical part of the rotational distribution and the vibrational distributions can be described by a prior function derived assuming that the internal modes of the alkyl substituent are not involved in any energy redistribution during the dissociation.
AB - Photodissociation of the molecules RNCS and RSCN (R = H, CH3, and C2H5) was investigated at 248 and 193 nm and the internal energy distributions in the CN resulting from the RS + CN fragmentation channel were probed by laser induced fluorescence. These CN distributions were identical for formation from the isomer pairs in agreement with an excited state isomerization postulated earlier. At 248 nm, all precursors lead to nearly thermal CN rotational distributions with rotational temperatures of approximately 1100 K in v = 0 and 800 K in v = 1. The vibrational distributions could not be characterized by the same temperatures. At 193 nm, contributions from two apparently different dissociation channels were observed. The CN rotational populations showed a narrow, strongly peaked distribution lying on a broad, approximately statistical distribution. For HNCS, this peak occurs near N = 10 suggesting dissociation from an excited state with a linear NCS skeleton. For the alkyl precursors, the peak occurs at very high rotational quantum number (N = 70) indicating an excited state with a bent NCS framework. Vibrational distributions with population out to v = 6 were observed. In all cases, the apparent statistical part of the rotational distribution and the vibrational distributions can be described by a prior function derived assuming that the internal modes of the alkyl substituent are not involved in any energy redistribution during the dissociation.
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U2 - 10.1063/1.459014
DO - 10.1063/1.459014
M3 - Article
AN - SCOPUS:0013633693
SN - 0021-9606
VL - 93
SP - 2346
EP - 2356
JO - The Journal of Chemical Physics
JF - The Journal of Chemical Physics
IS - 4
ER -