The gamma system of the nitric-oxide isotopomers ¹⁴N¹⁶O, ¹⁵N¹⁶O, ¹⁴N¹⁸O and ¹⁵N¹⁸O

Abstract

The spectra of the gamma (A ²∑⁺ - X²πr) system of the nitric-oxide isotopomers ¹⁴N¹⁶O, ¹⁵N¹⁶O, ¹⁴N¹⁸O and ¹⁵N¹⁸O, excited in the anode glow of a two-column hollow-cathode discharge tube of special design (Reddy and Prasad. J. Phys. E. Sci. Instr. 22, 306, 1989), were photographed in the spectral region 2140-2730 Å on a 2 m Bausch and Lomb spectrograph under medium resolution and the spectrum of ¹⁵N¹⁸O was also recorded on a 3.4 m Jarrell-Ash spectrograph under high resolution. The spectrum of ¹⁴N¹⁶O was obtained from the natural presence of nitrogen-14 and oxygen-16 of low pressure air in the discharge tube. The spectra of ¹⁵N¹⁶O and ¹⁴N¹⁸O were produced by admitting nitrogen-15 and oxygen-18 into the discharge tube, respectively. The spectrum ¹⁵N¹⁸O was produced by admitting a mixture of nitrogen-15 and oxygen-18 into the same discharge tube. The gamma system has been observed for the first time for ¹⁵N¹⁸O. -- For each of the isotopomers, six bands, namely, 1-0, 0-0, 0-1, 0-2, 0-3 and 0-4, each having four heads P₁₂ee, P₂₂ff/Q₁₂ef, P₁₁ee and P₂₁ff/Q₁₁ef, have been observed. The vibrational structures of the observed bands have been analyzed from the wavenumber data of the band heads of all the isotopomers of NO. In each case ∆G(1/2) of the A ²∑⁺ state and vibrational constants we and wexe of the X²π₃/₂ and X²π₁/₂ components of the ground electronic state have been determined. -- The rotational structure of the individual 0-1, 0-2 and 0-3 bands of the gamma system of ¹⁵N¹⁸O, photographed under high resolution, has been analyzed using the effective Hamiltonian proposed by Brown et al (J. Mol. Spectrosc. 74, 294, 1979) and a unique set of molecular constants has been obtained by the method of merging. The derived molecular constants in cm⁻¹ of ¹⁵N¹⁸O are: -- A ²∑⁺: ∆G(1/2)=2237.1 -- X²π: we=1819.15; wexe=12.870; Be=1.55644; αe=0.015343; De=4.5574x10⁻⁶. -- Also obtained for the X²π state are the values of Av, ADv, pV, qv for v = 1, 2, and 3 levels.