http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
2000 A absorption system of NH₃, ND₃, and NT₃
The absorption spectra in the 2000 A region of NH₃ and ND₃ taken by B. L. Landrum (1) and of NT₃ taken by J. R. Henderson (2) are examined, with emphasis on the temperature sensitive bands. Three new ND₃ and four new NT₃ bands are observed. While most of the previous band assignments are left unchanged, in this work one NH₃, three ND₃, and three NT₃ assignments are changed. New assignments are made for two ND₃ bands and two NT₃ bands. In the composite of Landrum's, Henderson's, and this work, the number of temperature sensitive bands identified is eight for NH₃, nineteen for ND₃, and eighteen for NT₃. Of the ND₃ bands, twelve correspond to transitions from ground state levels which involve [nu]"₁ or 2[nu]"₁ in combination with inversion levels. There are six levels of ND₃ known from infrared spectra which may be calculated from the present data. The average disagreement is about 2 cm⁻¹. In addition nine ground state vibrational levels have been determined which were not previously known. Except that fewer bands are observed for ND₃ and NT₃, results are similar to those of ND₃. The presence of [nu]"₁ in the "hot" bands leads one to expect the appearance of [nu]'₁ in the exited state. If [nu]'₁ is present, it is overlapped. Both NH₃ and ND₃ absorption intensifies for the (0000) <-- (0 v"₂ 00) transitions, where v"₂ = 0⁺, 1⁺, 2⁺, and 3⁺, are experimentally measured, and the corresponding relative intensities are calculated using the Franck-Condon Principle. The average disagreement is 17%. This is much lower than might be expected since the equilibrium H-N-H or D-N-D angles of the ground and exited states are 106°47' and 120° (3) respectively, and does support the Franck-Condon Principle. It is shown that over 80% of the overlap between ground and exited state vibrational wave functions occurs for an H-N-H or D-N-D angle variation of 120° - 117°, indicating that most of the transitions occur when the molecule is nearly planar. Since the transitions occur for such a small range of Q, the corresponding variation of R[subscript e](Q) is probably small. The exited state fundamental frequencies [nu]'₁ and [nu]'₃ for ND₃ and [nu]'₁, [nu]'₃, and [nu]'₄ for NH₃ and NT₃ are theoretically determined using the experimental; NH₃ -- ND₃ isotope shift and the faint bands in ND tentatively assigned to 2[nu]'₄.
Ph. D. in Physics Texas A & M University