Resonant interaction of a laser beam with a single droplet takes place if the
beam is absorbed in the droplet. Results are shown regarding the resonant interactions
of pulsed laser beams with microliter droplets in pendant position which contain
solutions of a laser dye-rhodamine 6G, phenothiazines (chlorpromazine, promazine),
hydantoin derivative [(5Z)-5-(3-chlorobenzylidene)-2-thioxo-4-imidazolidinone)] and
antibiotics (vancomycin), respectively, in water. A description of the electronic
structure of rhodamine 6G and chlorpromazine using Gaussian09 and GaussView 5.0
software is made. Exposure of droplets to laser radiation leads to generation of new
photoproducts that may have different properties if compared to parent compounds.
Such modifications are evidenced by laser induced fluorescence and thin
layer chromatography. In irradiated chlorpromazine water solution, out of
hundreds of photoreaction products, 5 were identified: promazine (PZ), promazine
sulfoxide (PZ-SO), 2-hydroxy promazine (PZ-OH), 2-hydroxy promazine
sulfoxide (PZ-OH-SO), chlorpromazine sulfoxide (CPZ-SO). For rhodamine 6G
solutions, the main results include the increasing intensity of LIF spectra in droplet
with respect to bulk, even if the volume of the cuvette for bulk measurements is much
higher than droplet’s volume. This behaviour may be explained by the confinement of
light inside droplet, where total internal reflection at surface occurs, the droplet being
associated with a spherical micro-optical resonator.
Keywords: Chlorpromazine, Droplet, Fluorescence, Hydantoins, Laser dye,
Lasing, Laser induced fluorescence, Promazine, Rhodamine 6G, Vancomycin,
Whispering gallery modes, WGM.
