This paper mainly concerns on nanosecond and femosecond laser spectroscopy of aromatic organic compounds as neurotransmitters, and plume diagnostics of the ablated species, in order to characterize the plasma dynamics, i.e. the temporal and spatial evolution of the plume. Optical emission spectroscopy has been applied to characterize the transient species produced in the femtosecond (fs) and nanosecond (ns) regimes. The laser sources employed for optical emission spectroscopy are a frequency-doubled Nd:YAG Handy (lambda = 532 nm, tau = 5 ns) and a frequency-doubled Nd:glass (lambda = 527 nm, tau = 250 fs). These studies aim to detect and give information on the photoexcitation and photodissociation of these biological molecules and to compare the plasma characteristics in the two ablation regimes. (c) 2007 Elsevier B.V. All rights reserved.