IR laser resonant desorption of polycyclic aromatic hydrocarbons

We investigate the resonant character of the laser desorption of polycyclic aromatic hydrocarbons (PAH) in the 3.3 μm range by exciting the C–H stretching with a tunable pulsed LiNbO3 optical parametric oscillator. A perfect match is obtained between the desorption yield and the optical absorption spectra of naphthalene, acenaphtene, and phenanthrene. The plume dynamics is probed by varying the delay between the desorption and ionization laser pulses. Simple calculations using Beer–Lambert and Hertz–Knudsen equations account for the absence of phase explosion mechanism and for the long desorption times observed. Analytical and technological openings of this resonant technique are discussed.