Laser-Induced Multidimensional Fluorescence Spectroscopy in Shpol'skii Matrixes with a Fiber-Optic Probe at Liquid Helium Temperature

Abstract

Improved methodology for chemical analysis via laser-excited Shpol'skii spectrometry at liquid helium temperature (4.2 K) is reported. Sample freezing is performed in a matter of seconds with the aid of a fiber-optic probe directly inserted into the liquid cryogen. Emission wavelength time matrixes, excitation emission wavelengths, and time-resolved excitation emission wavelengths are rapidly collected with the aid of a pulsed tunable dye laser, a high-resolution spectrograph, and an intensified charged-couple device. Data reproducibility for qualitative and quantitative analysis purposes and analytical figures of merit are demonstrated for several polycilic aromatic hydrocarbons/n-alkane systems. Fluorescence lifetime differences from analyte molecules occupying different crystallographic sites in the same frozen matrix are presented for the first time. The potential of our approach is illustrated for the direct analysis of a benzopyrene fraction typically encountered in HPLC analysis of polycyclic aromatic hydrocarbons.