Probing Electronic Dynamics during Photochemical Reactions

Abstract

This review discusses a new method for probing the evolution of the valence-electron structure of molecules during chemical reactions. The method relies on the interaction of an intense infrared laser pulse with molecules that results in the emission of attosecond pulses (1 as = 10–18 s) in a process known as high-harmonic generation. Time-resolved high-harmonic spectroscopy measures the phase and amplitude of attosecond pulses emitted from the reacting molecules through interference with the emission from the unexcited molecules. This coherent detection mechanism provides a high sensitivity to small excitation fractions and direct access to both the amplitude and the phase of attosecond pulses, the latter of which is otherwise very difficult to measure. These observables reveal several complementary aspects of excited-state photochemical dynamics such as dissociation, adiabatic wave-packet evolution and conical intersection dynamics.

Ab initio calculation of femtosecond-time-resolved photoelectron spectra of NO2 after excitation to the A-band

“…The spectroscopic properties of NO 2 have been determined with high accuracy [1][2][3][4][5][6][7][8][9] . However, femtosecond time-resolved experiments have only recently become possible with the introduction of multiphoton time-resolved photoelectron spectroscopy (MP-TRPES) [10][11][12][13][14][15] (for a review, see 16 ) and time-resolved high-harmonic spectroscopy (TRHHS) [17][18][19][20][21][22] . Whereas these techniques could be realized with state-of-the-art femtosecond lasers, their interpretation is sometimes challenging because of the high peak intensities associated with femtosecond laser pulses.…”