Broad-Band Impulsive Vibrational Spectroscopy of Excited Electronic States in the Time Domain.
We demonstrate that transient absorption spectroscopy performed with an ultrashort pump pulse and a chirped, broad-band probe pulse is capable of recording full vibrational spectra of excited electronic states in the time domain. The resulting spectra do not suffer from the nontrivial baselines and line shapes often encountered in frequency domain techniques and enable optimal and automated subtraction of background signatures. Probing the molecular dynamics continuously over a broad energy bandwidth makes it possible to confidently assign the vibrational coherences to specific electronic states and suggests the existence of mode-specific absorption spectra reminiscent of resonance Raman intensity analysis. The first observation of the nominally forbidden one-photon ground to first excited electronic state transition in β-carotene demonstrates the high sensitivity of our approach. Our results provide a first glimpse of the immense potential of broad-band impulsive vibrational spectroscopy (BB-IVS) to study ultrafast chemical reaction dynamics.
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
Matz
M
Liebel
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
Philipp
P
Kukura
carotenoids; femtosecond Raman; time domain vibrational spectroscopy; ultrafast spectroscopy; vibrational coherence