Multi-wavelength thermal lens spectrophotometer

Abstract

A novel four-wavelength pump-probe configuration thermal lens spectrophotometer that is capable of simultaneously measuring thermal lens signals at four different wavelengths has been developed. The four excitation beams were derived from the same argon ion laser, which operated in a multi-line mode. The sample was sequentially excited by these four and the corresponding thermal lens signals were monitored by a He-Ne laser. Compared with other existing thermal lens apparatus, this four-color spectrophotometer has advantages that include its ability to provide identification of the analyte (as the ratios of the signals at four different excitation wavelengths) and to analyze simultaneously four-component samples without the need for any prior sample preparation. With this apparatus and with the use of 6-mW excitation beams modulated at 1.02 Hz, the detection limit for four-component samples is estimated to be about 10 −9 M, which is similar to the detection limit obtained for a one-component sample using a single-wavelength system.