Photoelectron spectroscopy of HNO- and DNO-

We have obtained the photoelectron spectra of HNO- and DNO- using a recently constructed negative ion photoelectron spectrometer. We observe detachment to three different electronic states of HNO and DNO, namely the X 1A', a 3A'', and A 1A'' states. The electron affinity of HNO is determined to be 0.338 +- 0.015 eV while that of DNO is 0.330 +- 0.015 eV. The a 3A'' state, which has not been observed directly before, is found to lie 0.778 +- 0.020 eV above the X 1A' state in HNO and 0.785 +- 0.020 eV in DNO. We see vibrational excitation up to #betta#'2 = 3 of the #betta#2 (N--O stretch) mode in the HNO and DNO X 1A' state. In the a 3A'' and A1 A'' states, we see excitation of both #betta#2 and #betta#3 (H--N--O bend) modes. The fundamental frequencies for the a 3A'' state are #betta#2 = 1468 +- 140 cm-1 and #betta#3 = 992 +- 150 cm-1 for HNO and #betta#2 = 1452 +- 140 cm-1 and #betta#3 = 750 +- 140 cm-1 for DNO. Analysis of transitions from vibrationally excited ions gives a #betta#2 fundamental frequency of 1153 +- 170 cm-1 in HNO- and 1113 +- 170 cm-1 in DNO-. A study of the angular distribution of the photodetached electrons yields the values of #betta#, the anisotropy parameter, for the various transitions in the spectrum. A Franck--Condon factor analysis of the HNO X 1A' band results in an estimate of the N--O bond length in the negative ion of 1.33 +- 0.02 A