The thermal decompositions of 2-azidoethanol and 2-azidoethyl acetate have been studied by matrix isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. The products that were detected in a flow system at different temperatures (CH2NH, H2CO, N2, CO, and HCN from N3CH2CH2OH and C2H4, CH2NH, HCN, CO2, and N2 from N3CH2COOCH2CH3) allowed mechanisms for decomposition to be proposed. The experimental evidence obtained is consistent with 2-azidoethyl actetate decomposing via a concerted mechanism, similar to that found previously for azidoacetic acid, whereas the 2-azidoethanol decomposition is consistent with a stepwise decomposition mechanism as observed previously for azidoacetone.

The BrO radical, prepared by the BrϩO 3 reaction, has been investigated by ultraviolet photoelectron spectroscopy. Two vibrationally resolved bands were observed corresponding to the ionizations BrO ϩ (X 3 ⌺ Ϫ )←BrO(X 2 ⌸) and BrO ϩ (a 1 ⌬)←BrO(X 2 ⌸). These assignments are supported by the results of complete active space self-consistent field/multireference configuration interaction ͑CASSCF/MRCI͒ calculations performed as part of this work. The adiabatic ionization energies of these bands were measured as (10.46Ϯ0.02) and (11.21Ϯ0.02)eV, respectively. Measurement of the vibrational separations in these bands led to estimates of the vibrational constants in the ionic states of (840Ϯ30) cm Ϫ1 and (880Ϯ30) cm Ϫ1 , and Franck-Condon simulations of the vibrational envelopes gave values of the ionic state bond lengths of (1.635Ϯ0.005) and (1.641Ϯ0.005) Å for the X 3 ⌺ Ϫ and a 1 ⌬ states of BrO ϩ , respectively. The OϩBr 2 reaction was found to give a band at (10.26Ϯ0.02) eV associated with a reaction product. Comparison of the results obtained for the BrϩO 3 reaction showed that it could not be assigned to ionization of BrO. Calculations of the first adiabatic ionization energies and Franck-Condon simulations of the vibrational envelopes of the first photoelectron bands of BrO 2 and Br 2 O and their isomers demonstrated that this band corresponds to the first ionization of OBrO, the BrO 2 ϩ (X 1 A 1 )←BrO 2 (X 2 B 1 ) ionization. FranckCondon simulations were performed with the experimental geometry of BrO 2 (X 2 B 1 ) but with different cationic state geometries. The simulated envelope which most closely matched the experimental envelope gave geometrical parameters of r e ϭ1.6135 Å and ЄOBrOϭ117.5°for the ionic state.

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Photoionization of the OH and OD radicals, produced from the H+NO2 and D+NO2 reactions, has been studied in the gas phase in the photon energy region 13.0–17.0 eV using constant ionic state (CIS) and photoelectron spectroscopy (PES) employing synchrotron radiation. Structure in the CIS spectra, recorded for the first and second photoelectron bands, has been assigned to excitation to (a 1Δ,3d) and (A 3Π,3d) Rydberg states. A comparison of vibrationally specific OH and OD CIS spectra, and photoelectron spectra recorded at resonant wavelengths, has allowed a more complete assignment of structure observed in earlier photoionization mass spectrometric measurements. These assignments have been supported by the results of Franck–Condon calculations. The CIS spectra have been shown to be dominated by structure arising from excitation from the outermost valence molecular orbitals of OH [the nonbonding 1π(O 2p) orbital and the bonding 3σ orbital] to O nd Rydberg orbitals. Photoelectron spectra recorded for the first bands of OH and OD at resonant photon energies have allowed more extensive vibrational structure to be obtained than has previously been recorded by PES experiments performed with inert gas discharge photon sources.

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