Author Institution: Department of Physics, The Ohio State University, Columbus Ohio, 43210-1106, USA; Department of Physics and Centre for Laser, Atomic, and; Molecular Sciences, University of New Brunswick, P.O. Box 4400; Fredericton NB E3B 5A3, Canada; Canadian Light Source, Inc., University of Saskatchewan; Saskatoon, SK, Canada
The first vibrational overtone spectrum of solid parahydrogen with various low orthohydrogen impurity levels has been studied in the range 7900--10 000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ using a White-type external multireflection system with a 34.8-cm sample path length. We were able to detect extremely weak features, namely, the ${\mathrm{Y}}_{1}$(0) at 7991.85 (1) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, and the double transitions ${\mathrm{U}}_{1}$(0) + ${\mathrm{Q}}_{1}$(1), ${\mathrm{U}}_{1}$(0) + ${\mathrm{S}}_{1}$(0), ${\mathrm{U}}_{1}$(1) + ${\mathrm{Q}}_{1}$(0), and ${\mathrm{Q}}_{1}$(0) + ${\mathrm{Q}}_{1}$(0). The ${\mathrm{Q}}_{1}$(0) + ${\mathrm{Q}}_{1}$(1) and ${\mathrm{Q}}_{1}$(1) + ${\mathrm{Q}}_{1}$(1) double transitions were resolved. We obtained a rich orthohydrogen satellite spectrum associated with the transitions ${\mathrm{Q}}_{2}$(0) and ${\mathrm{Q}}_{2}$(1) near 8060 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. An analysis and assignment of these satellite transitions are presented. The double transitions of the type ${\mathrm{Q}}_{1}$(J) + ${\mathrm{Q}}_{1}$(${\mathrm{J}}^{|\mathrm{I}\mathrm{H}}$) (J,${\mathrm{J}}^{|\mathrm{I}\mathrm{H}}$ = 0,1) are located in the spectral region around 8300 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The most remarkable features here are the ${\mathrm{Q}}_{1}$(1) + ${\mathrm{Q}}_{1}$(1) transition, which consists entirely of fine structure, and the ${\mathrm{Q}}_{1}$(0) + ${\mathrm{Q}}_{1}$(0) transition, which, to our knowledge, has an intensity that cannot be accounted for by previously proposed mechanisms. Finally the thermal shift of all of the above-mentioned transitions was investigated by lowering the sample temperature from 12.5 K down to 6.5 K while taking spectra. The influence of the change of temperature on the line positions, linewidths, and interaction parameters of solid hydrogen is discussed.
We discuss past and recent progress in our long-term laboratory program concerning the submillimeter-wave rotational spectroscopy of known and likely interstellar molecules, especially those associated with regions of high-mass star formation. Our program on the use of spectroscopy to study rotationally inelastic collisions of interstellar interest is also briefly mentioned.
The microwave spectrum of the deuterated form of fulminic acid (DCNO) has been investigated in the frequency region from 9 to 42 GHz. For the ground vibrational state of DCNO the following rotational constants were obtained: B 0 (D 12 C 14 N 16 O) =10 292.50 MHz, B 0 (D 13 C 14 N 18 O) =10 011.66 MHz, B 0 (D 12 C 14 N 18 O) = 9 758.87 MHz. The corresponding moments of inertia yield a combined r s and r 0 structure: r DC = 1.027 ±0.001 Å, r CN = 1·168 ±0.001 Å, r NO = 1.199 ± 0.001 Å. For the two degenerate bending modes ν 4 and ν 5 the l-type doublets of the transition J = 1 - 2 and the two corresponding series of l-type doubling transitions have been observed. The analysis of the two l-type doubling series revealed that P 4 and P 6 centrifugal distortion contributions are sufficient to account for the spectrum. The doubling constants given in MHz are q 4 = 17.9103-(0.6467 · 10 -4 )J(J + 1) +(0.188 · 10 -8 ) [J(J + 1)] 2 , q 5 = 38.0907-(0.3061 · 10 -3 )J(J + 1) + (0.314 · 10 -8 )[J(J + 1) ] 2 . A third series of l-type doubling transitions arising from the II-level of the ν 5 =3 vibrational state has been found and analysed, yielding: q (0) 3×5 =29.2748 ± 1.8 · 10 -4 MHz; E Φ -E II =Δ ≅ 41 cm -1 .
The low-lying CCN bending mode of cyanofulminate, NCCNO, was characterized by rotational spectroscopy in the millimeter-wave and submillimeter-wave range as well as by rovibrational spectroscopy in the far-infrared range. The spectra exhibit the gross features of a linear molecule. However, a closer qualitative analysis regarding the low-lying CCN bending mode revealed significant deviations from a harmonic bending mode that is normally found in a linear molecule. This result was confirmed by a quantitative analysis of the combined data with an effective Hamiltonian for a linear molecule. In linear molecule notation, the term value of the first excited state ν7 is 80.524 182 (10) cm-1, and the term values for the l7 = 0 and l7 = 2 levels of the second excited state 2ν7 are 166.118 254 (16) and 164.604 243 (22) cm-1. A semirigid bender analysis of our data, including rotational transitions of the isotopomers 15NCCNO, N13CCNO, NCC15NO, and NCCN18O observed in natural abundance, yielded a considerable quartic contribution to the effective CCN bending potential function V(ρ)/cm-1 = 747.40 (81) × (ρ/rad)2 + 959.2 (24) × (ρ/rad)4.
Abstract The rotation‐inversion spectrum of isocyanamide, H 2 N — NC, has been investigated in the frequency range 100 to 400 GHz. Due to the near C 2v symmetry of the inverting molecule two types of dipole transitions have been observed: 1) intrasystem a‐type transitions and 2) intersystem or rotation‐inversion c‐type transitions connecting the two energy manifolds of H 2 N — NC belonging to the inversion states O + and O − , respectively. The inversion splitting was found to be 0.369 cm −1 , indicative of a high barrier to inversion. Pure inversion transitions are not allowed. The rotation‐inversion analysis was carried out for 240 a‐type and c‐type transitions using S‐reduced Hamiltonians according to Watson for the O + and O − inversion states separated by the inversion splitting E 1nv . The analysis yielded the following spectroscopic constants: magnified image plus centrifugal distortion constants. The present data and their analysis provide an excellent basis for a radioastronomical search for H 2 N — NC.
The rotational spectra of three isotopic species of HNC have been observed in the millimeter wave region. In the case of the parent species, H 14 N 12 C, our measurement of the J = 1←0 transition unequivocally confirms the assignment of the U90.7 interstellar line to HNC. For the parent species the molecular constants obtained are B 0 = 45332.005(40) MHz and D 0 = 0.1019(50) MHz. Structural parameters derived from the ground state rotational constants of this linear molecule are r(H-N) = 0.987 (3) Å and r(N-C) =1.171 (4) Å.
