Femtosecond transient absorption microspectrophotometer combined with optical trapping technique

A transient absorption microspectroscopic system with 200-fs temporal and micrometer (<2.5 μm) spatial resolutions was developed by using a microscope and a laser trapping technique. A pump beam, a white-light continuum generated by focusing an intense femtosecond laser pulse into water, and a trapping laser beam were coaxially introduced into a microscope and focused onto a sample by a reflecting objective lens. Advantages of a reflecting objective lens are discussed for the measurements of transient absorption spectra. This method was applied to a dye-doped single liquid droplet in water and α- and β-perylene single microcrystals.