Josef Pliva

Molecular constants of nitrous oxide, 14N216O

Abstract The zero-order frequencies, anharmonic and vibration-rotation coupling constants up to fourth order have been calculated for the molecule of nitrous oxide, 14N216O, from a careful analysis of all available experimental data on the vibration-rotation energy levels of the molecule. It was found inevitable to include the fourth-order constants in the energy expression in order to reproduce the recent accurate measurements to within their experimental uncertainties. A thorough study has been made of the various anharmonic interactions influencing the energy levels. To obtain a stable solution for the molecular constants in a least-squares adjustment to the observed energy levels involved in these interactions, it was found necessary to treat the vibrational (J = 0) and vibrational-rotational (J > 0) terms simultaneously; a general procedure effecting this calculation is described in detail. With the inclusion of the Fermi interaction connected with matrix elements of the type 〈v 1 v 2 lv 3 J∥v 1 −1v 2 +2 lv 3 J〉 the observed levels up to 5700 cm−1 could be reproduced with a standard deviation of 0.006 cm−1. On the other hand, to attain a satisfactory fit also for the high levels observed in the photographic infrared region (8700 to 12000 cm−1), additional interactions of the type 〈v1v2lv3 | v1-2 v2l v3+1〉 had to be taken into account. However, the values obtained for the constants respousible for these interactions are not considered entirely satisfactory due to the somewhat inferior accuracy of the available photographic infrared data.

Infrared spectra of isotopic nitrous oxides

Abstract The infrared spectra of 15 N 14 N 16 O and 15 N 2 16 O have been measured with a high-resolution grating spectrometer in the region between 2100 and 4450 cm −1 . The spectrum of the ordinary species, 14 N 2 16 O, was remeasured for comparison in order to obtain accurate values of the isotopic displacements. Twelve vibration-rotation bands of each isotopic species have been analyzed. From the rotational constants obtained it was possible to determine improved equilibrium internuclear distances ( r NN 1.1282 A , r NO 1.1842 A ) for the nitrous oxide molecule.

Dideuteroacetylene bands in the 2–2.5 and 5–10 micron regions

Abstract Improved measurements of the 12C2D2 bands occurring in the 2–2.5 μ and 5–10 μ regions are reported. An internally consistent set of molecular constants that best represents all the available experimental data on the infrared bands of this molecule was determined with the aid of a computer program written for this purpose.

Unambiguous analysis of three-spin 12 spectra

Abstract A method of calculating the chemical shifts and spin-spin coupling constants (NMR parameters) of an ABC system from sets of experimental frequencies obtained by measuring the transitions of the system at two different operating frequencies is described. Simultaneous treatment of such sets of data makes it possible to obtain, for the NMR parameters, a set of algebraic equations which yield a unique solution of the problem (except for the absolute signs of the spin-spin coupling constants and the structural assignment).