Femtochemistry of Norrish Type‐I Reactions: IV. Highly Excited Ketones—Experimental

Symmetry, vibrational energy redistribution and vibronic coupling: The internal conversion processes of cycloketones

“…Thus, some higher order couplings must be of opposite sign. As expected on the basis of the size of the coefficients, the largest coupling is found for ν 16 . Figure 6(b) shows the Fourier-transform of the total interstate coupling for the first 5 ps and the subsequent 20 ps of the propagation.…”

“…In the long time spectrum, peaks which can be directly associated with spreading and contracting motion in ν 1 and ν 3 are observed at ∼420 cm −1 and ∼1060 cm −1 . The peak ∼1150 cm −1 is most likely due to a bilinear coupling involving ν 1 and ν 28 , whereas the peak at ∼1510 cm −1 is due to a third order coupling involving ν 3 and ν 16 .…”

“…Figure 6(b) shows the Fourier-transform of the total interstate coupling for the first 5 ps and the subsequent 20 ps of the propagation. For both time periods, the largest amplitude component is found with a frequency ∼2070 cm −1 , which corresponds to the frequency of the standard deviation of the position operator for ν 16 given by δQ i = Q 2 i − Q i 2 . It is thus the spreading and contracting motion of the wave packet in ν 16 , which leads to the largest modulation of the interstate coupling.…”

“…For both time periods, the largest amplitude component is found with a frequency ∼2070 cm −1 , which corresponds to the frequency of the standard deviation of the position operator for ν 16 given by δQ i = Q 2 i − Q i 2 . It is thus the spreading and contracting motion of the wave packet in ν 16 , which leads to the largest modulation of the interstate coupling. In the short time spectrum, peaks are also observed at ∼1220 and ∼1530 cm −1 , which are related to couplings involving ν 16 in combination with ν 1 and ν 3 , respectively.…”

“…1,[11][12][13][14][15][16][17] Initial processes involve internal conversion from a Rydberg state to the (n, π *) state, the lowest lying excited singlet state. This is sometimes referred to as predissociation dynamics due to the eventual fate of the molecules.…”