Two-photon spectroscopy of PbMoO4 single crystals: indirect interband transitions

Two-photon interband absorption spectra are obtained first in PbMoO4 crystals. They are shown to be attributed to indirect two-photon absorption (TPA) with the assistance of phonons to exciton state formed band transitions with the extrema in different points of the Brillouin zone. The energy parameters of excitons Eexi = 3.56 (80 K) and 3.53 eV (300 K), Ebi = 50 meV, of phonons (65, 180, and 270 meV), and of the interband absorption edge Egi = 3.61 (80 K) and 3.58 eV (300 K) are obtained. Anomalously high efficiency of electron–phonon interaction is found in crystals studied. The phonon energy observed in TPA at indirect transitions is shown to be determined probably by joint participation of several active phonon modes of MoO4−2 tetrahedral group in PbMoO4 crystal. [Russian Text Ignored].