Wavelength dependence of UV-laser induced emission of neutral and ionic species from single crystal NaNO3

We report time-resolved, quadrupole mass-selected measurements of neutral and ion emission from single crystal sodium nitrate exposed to ns pulse excimer laser radiation at 157 nm (F2 excimer, 7.9 eV photons), 193 nm (ArF excimer, 6.4 eV photons) and 248 nm (KrF excimer, 5.0 eV photons). Neutral emissions, including NO, O2, N2, and Na are observed at all three wavelengths. At 193 nm, intense atomic N and O emissions are also observed, possibly due to a 1+1 excitation involving the π∗←π transition in the nitrate ion (centered at 6 eV) followed by excitation to a higher excited state. This transition is not efficiently excited at the other two wavelengths. At 248 nm, much of the emission is attributed to thermally assisted, dissociative electron/hole attachment. Although 157 nm photons do not excite the π∗←π transition efficiently, the resulting NO emission is found to be quite intense: on a per unit energy (or per photon) basis, 157 nm photons are much more efficient in decomposing nitrate anions than 193 nm photons. Intense ion emission (principally Na+ and NO+) is observed at 193 and 157 nm, with weaker Na+ emission at 248 nm. The ion intensities show high-order fluence dependence, consistent with photoelectronic emission involving sequential photon absorption as described earlier for 248 nm irradiation [J. Appl. Phys. (80) (1996) 6452].