Selective isomerization of butadiene-cyclobutene systems via infrared multiphoton excitation

Frequency‐dependent branching ratio in the infrared multiphoton photochemistry of diethyl carbonates

“…When the total yields are identical (entry 2 vs entry 5), the branching ratio is considerably smaller for reaction at P (14) ( p = 1.26 2 0.17) than for reaction at P(38) (0 = 1.63 2 0.15). In spite of scatter in the data, these two values are significantly different in the 99.9% confidence level by a standard t-test [the total number of degrees of freedom was 19; 8 runs at P(38), 13 runs at P (14)]. When the two frequencies are compared at the same fluence (entry 4 vs entry 5 ) , the differences are even greater.…”

“…Parameters for the calculation of individual RRKM rate constants, k~p ) ( E ) , are given in the Appendix. culated branching ratio gives ( E , ) = 99 kcalmol-' at P (14) and ( E , ) = 7 1 kcalmol-' at P(38). The absolute magnitudes of these energies have fairly large uncertainty owing to the uncertainty in the Arrhenius parameters.…”

“…Two ad hoc ways to build the required flexibility into the model would be first to postulate an inhomogeneous sample incorporating subsets of absorbing ('hot') molecules and non-absorbing ('cold') molecules, 28829 and allow the relative populations of the subsets to change with frequency . In the case of DEC-ds, a larger fraction of the sample would be required in the absorbing (hot) population at P(38) but, because of the smaller value of Zao, the average energy of the absorbing population lags behind that for P (14). Secondly, permit y to be frequency dependent.…”

Quantum dynamical study of molecular overtone transitions induced by intense laser radiation

“…Following the numerical solution of the coupled Schr6dinger equation (7) over the first optical cycle, (11)(12)(13) and (8) can be used to calculate the long-time average transition probability [20] 1 S"…”

“…The multiphoton technique has also proved useful in exciting the internal modes of molecules and enhancing their reactivity [I, 3]. Furthermore, intense infrared lasers have been used recently to excite vibrational overtone transitions [5][6][7][8] and induce molecular isomerization [9][10][11][12].…”