Two Photon Spectroscopy of Dipole Forbidden Transitions III. Experimental Determination of Two Photon Absorption Spectra Including Polarization Control


  • For Parts I and II see References [3] and [4].


A new experimental technique is described which allows the measurement of two-photon absorption spectra of luminescent molecules and simultaneously the evaluation of the two-photon polarization parameter Ω over a wide spectral range. The resolution obtained is comparable to conventional UV absorption and polarization spectra. Examples are shown for different types of unsaturated hydrocarbons. The influence of S1 → Sm excitations and of variations of the profile of the exciting laser pulse are discussed. It is shown that careful control of both the quadratic nature of the two-photon process and the beam profile is essential to avoid artificial features in wide range two-photon spectra.