LIGHT-INDUCED SINGLE-MOLECULE FREQUENCY-SHIFT

Alight induced frequency shift of the 0-0 line was measured in two-pho ton excitation spectra of single diphenyloctatetraene molecules doped in a crystal matrix. The shifts were proportional to the laser power w ith a slope of about 600 MHz/W when the laser beam of about 300 mW pow er was focused to a diameter of 2 mu m. Significantly, the observed li ne broadenings were an order of magnitude smaller than the shifts. The effect is ascribed mainly to a ''fast'' energy exchange between a loc al vibration and thermal phonons created by the third harmonic C-H ban d absorption in the matrix, and partially to an ac Stark shift.