SATURATION SPECTRUM OF THE NU(2) NU(4) DYAD OF ASH3/

The v(2)/v(4) dyad of arsine, AsH3, has been investigated between 875 and 1100 cm(-1) by laser sideband spectroscopy. In total 189 transitio ns have been observed with sub-Doppler resolution (approximate to 300 kHz) and measured to an absolute accuracy of about 100 kHz. These data may be useful to serve as a secondary frequency standard. Our observa tions include four perturbation-allowed transitions with Delta(k - l) = 3. Saturation spectra of dipole forbidden transitions had not been p reviously reported for arsine. Quadrupole hyperfine structure, as well as vibration-rotation splitting of \k - l\ = 3N levels in both fundam entals, has been analyzed. Combining our results with MW and RF data ( 239 frequencies) reported in the literature, a total of 882 transition frequencies were available to fit 15 ground state parameters and 48 e xcited state parameters of the v(2)/v(4) dyad. The standard deviation of the fit is 245 kHz. (C) 1998 Academic Press.