Spectroscopy and femtosecond dynamics of the ring opening reaction of 1,3-cyclohexadiene

Abstract

The early stages of the ring opening reaction of 1,3-cyclohexadiene to form its isomer 1,3,5-hexatriene, upon excitation to the ultrashort-lived 1 1B2 state, were explored. A series of one-color two-photon ionization/photoelectron spectra reveal a prominent vibrational progression with a frequency of 1350 cm(-1), which is interpreted in a dynamical picture as resulting from the ultrafast wave packet dynamics associated with the ring opening reaction. Photoionization in two-color three-photon and one-color four-photon ionization schemes show an ionization pathway via the same ultrashort-lived 1 1B2 state, and in addition, a series of Rydberg states with quantum defects of 0.93, 0.76, and 0.15, respectively. Using those Rydberg states as probes for the reaction dynamics in a time-resolved pump-probe experiment provides a direct observation of the elusive 2 1A1 state that has been implicated as an intermediate step between the initially excited 1 1B2 state and the ground electronic state. The rise and decay times for the 2 1A1 state were found to be 55 and 84 fs, respectively.

Ultrafast Dynamics of 1,3-Cyclohexadiene in Highly Excited States

“…The present work demonstrates that RFS is able to observe not only kinetic transitions between populations of molecules in different energy wells, as has been done in the past [7], but also the time-dependent dynamical motions in essence, the technique captures the geometrical aspect of the time-propagating wave packet and thereby serves as a method to measure ultrafast structural dynamics. While the computation of Rydberg electron binding energies is not yet sufficiently advanced to invert spectra to derive and determine molecular structures, the experiments on CHD show that RFS is a viable method to measure ultrafast structural dynamics.…”

“…Upon excitation to the 1B valence state, the reaction path carries the molecule within about 140 fs along the ring-opening coordinate through the 1B/2A and 2A/1A conical intersections back to the ground state [3][4][5][6][7]. But even while these curve-crossing transitions are now well understood, numerous questions remain.…”

Theory and computations of two-photon absorbing photochromic chromophores

“…The dynamics of the cycloreversion in the CHD/HT system was repeatedly studied with the time-resolved ultrafast spectroscopy techniques [19,168]. The results are summarized in Ref.…”

Theoretical Photochemistry of the Photochromic Molecules Based on Density Functional Theory Methods

“…Dynamics of cycloreversion in the CHD/HT system was repeatedly studied with time-resolved ultrafast spectroscopy techniques [12,32]. The results are summarized in Ref.…”