Journal of Physical Chemistry A, Vol.113, No.26, 7439-7450, 2009
Phase Sensitive Control of Vibronic Guest-Host Interaction: Br-2 in Ar Matrix
Vibronic progressions are programmed into a pulse shaper which converts them via the inherent Fourier transformation into a train of femtosecond pulses in time domain for chromophore excitation. Double Pulse results agree with phase-sensitive wave packet superposition from a Michelson interferometer which delivers coherence times with high reliability. Spectral resolution of 1 nm and a spacing of around 4 nm within the 20 nm envelope centered at 590 nm delivers a train of seven phase-controlled 40 fs subpulses separated by 250 fs. Combs adjusted to the zero phonon lines (ZPL) and phonon sidebands (PSB) of the B state vibronic progression are reproduced in the chromophore for a coherent subpulse accumulation. B state ZPL wave packet dynamics dominates in pump-probe spectra due to its coherence despite an overwhelming but incoherent A state contribution in absorption. PSB comb accumulation is also phase sensitive and demonstrates coherence within several 100 matrix degrees of freedom in the vicinity.