Calorimetric standards for photothermal methods in ultraviolet and visible spectral regions

Abstract

Utilizing a time-resolved thermal lensing (TRTL) technique coupled with laser flash excitation, we have determined the heat conversion efficiency, a, of photoexcited molecules in solution at room temperature. The efficiencies of pyridazine, dicumarol, and 8-quinolinol are unity in the ultraviolet region. Azulene is demonstrated to be a good calorimetric standard in the visible region. The solvent effect on the thermal lens signal is well explained by thermal properties of solvent molecules, i.e. the cubic expansion coefficient and the specific heat capacity.