Laser induced electron and sodium ion emission from single crystal NaNO3 at 1064 nm

Wide band gap insulators irradiated with UV pulsed lasers have been shown t o yield both photoinduced electrons and energetic positive ions suggesting occupied electronic states in the band gap. It is not obvious that similar experiments with near-IR wavelengths should yield detectable emissions. Her e we report electron and Na+ ion emission from single crystal sodium nitrat e (similar to 10 eV band gap) upon exposure to near-IR (1.16 eV) laser radi ation. The fluence dependence of both ion and electron yields is highly non linear and the kinetic energies of the emitted ions can reach values up to 5 eV. Our data suggest that the observed emissions originate from defect si tes and they are consistent with a model that requires multiple single phot on charge transfer to ionize an electron trap and subsequently eject a near by positive adion due to electrostatic repulsion. Further evidence for the role of defects in the observed ion emission are provided by two beam exper iments; one beam (UV laser) is used to generate defects and the second beam (near-IR laser) is used to photodesorb the ions. Such experiments demonstr ate that exposure of the sodium nitrate surfaces to UV laser radiation sign ificantly increases the ion emission due to near-IR laser radiation. (C) 20 00 American Institute of Physics. [S0021-8979(00)06503-8].