Resonant uv pump-probe spectroscopy of dipicolinic acid via impulsive excitation
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We present experimental evidence of coherent wave packet motion in dipicolinic acid (C7 H5 N O4) which is an important marker molecule for bacterial spores. Resonant impulsive excitation is achieved by applying a uv pump pulse (267 nm, 16 fs) which has a duration that is shorter than the vibrational period of the molecules. The resulting dynamics is then probed with a weaker pulse of the same width and frequency. Evidence of the important "fingerprint" region for this molecule (between 1000 cm-1 and 1500 cm-1) is found in the transient absorption of the probe. We present simulations of the pump-probe experiment, based on the Liouville equation for the density matrix, and predict the optimal pulse width and detuning. 2008 The American Physical Society.