Two-photon spectroscopy in KCl using synchrotron radiation

Two-photon absorption spectra in the excitonic region of KCl up to 8.65 eV are reported. The sources employed in the two-photon experiment are the synchrotron radiation together with a neodymium-doped yttrium aluminum garnet laser. The measured absorption spectra show structures attributed to the 2p and 3p exciton levels associated with the direct gap of KCl. These optical data give a direct measurement of the energy gap and an estimation of the exciton mass of KCl.