Abstract

We present a technique for standoff trace chemical sensing that is based on the dependence of excited electronic state lifetimes on the amount of internal vibrational energy. The feasibility of the technique is demonstrated using N,N-dimethylisopropylamine (DMIPA). Time-resolved measurements show that the lifetime of the $S_1$ state in DMIPA exponentially decreases with the amount of vibrational energy. This property is employed to acquire molecular spectral signatures. Two laser pulses are used: one ionizes the molecule through the $S_1$ state; the other alters the $S_1$ state lifetime by depositing energy into vibrations. Reduction of the $S_1$ state lifetime decreases ionization efficiency that is observed by probing the laser-induced plasma with microwave radiation.

© 2013 Optical Society of America

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