Romola D'Cunha

High resolution diode laser measurements on the ν2 bands of 14NH3 and 15NH31

Abstract More than 500 lines in the ν2 bands of 14NH3 and 15NH3 have been measured in the region 740–1200 cm−1 with a diode laser spectrometer, with an accuracy better than 0.0005 cm−1 for most of the lines. Wavenumbers (in cm−1) were determined using a 3-in. Ge etalon for calibration and OCS, N2O, NH3, and CO2 lines as references. The diode laser data were combined with pure inversion and inversion rotation frequencies and sets of rotational constants were obtained by the method of merged least squares. Perturbations between the Δk = ±3 levels have been taken into account in these calculations.

Analysis of the high-resolution spectrum of acetylene in the 2.4 μm region

Abstract The high-resolution Fourier transform spectrum of acetylene in the 2.4 μm region has been obtained at an apodized resolution of 0.0054 cm −1 . In the analysis of the ( ν 1 + ν 4 + ν 5 ) 2.0 ← ν 4 1 and ( ν 1 + 2 ν 5 ) 2.0 ← ν 5 1 hot bands occurring in this region, the vibrational and rotational l -type resonances have been explicitly taken into consideration. The spectral data have been fitted with residuals approaching the experimental accuracy and molecular parameters have been obtained for the bands investigated. The present studies have also shown that the assignments of the ( ν 1 + ν 4 + ν 5 )(Σ u − ) ← ν 4 (Π g ) and ( ν 1 + ν 4 + ν 5 )(Δ u ) ← ν 4 (Π g ) subbands reported by previous workers must be interchanged.

Absorption intensities of zero-phonon single and double transitions in the multipole-induced spectrum of solid hydrogen

Abstract The theory of absorption intensities of some zero-phonon single and double transitions in solid H 2 is discussed. General expressions are developed for the integrated absorption coefficients of (i) the single transitions ( v ′ = v , J ′ = l) ← ( v ″ = 0, J ″ = 0) in solid para -H 2 and ( v ′ = v , J ′ = l + 1) ← ( v ″ = 0, J ″ = 1) in ortho -H 2 interspersed in a matrix of solid para -H 2 , and (ii) the double transition [( v ′ = v 1 , J ′ = l) ← ( v ″ = 0, J ″ = 0)] + S v 2←0 (0) in solid para -H 2 .

Normal coordinate analysis of CF3H and CF3D molecules

A rigorous normal coordinate analysis is made for the molecules CF3H and CF3D using all the available vibrational data: 12 frequencies, 4 Coriolis coupling constants and 3 centrifugal stretching constants. 2 types of force fields have been obtained: a General Harmonic Force Field with 12 parameters and a modified Urey-Bradley Force Field with 9 parameters. Both the force fields account for the observed data reasonably well.

The a2ν2 ← sν2 bands of 14NH3 and 15NH3

Abstract Numerous transitions belonging to the a 2 ν 2 ← sν 2 hot bands of 14 NH 3 and 15 NH 3 have been identified and assigned in the long-path Fourier transform spectra of ammonia. The data have been processed to obtain effective molecular parameters for the a 2 ν 2 states of 14 NH 3 and 15 NH 3 .

High-J transitions in the ν2 bands of 14NH3 and 15NH3

Abstract The Fourier transform spectra measured using the multiple reflection absorption cell with a path length of 192 m are reported for the high- J transitions of the ν 2 bands of 14 NH 3 and 15 NH 3 . More than 400 transitions which have been assigned for the first time in both 14 NH 3 and 15 NH 3 represent nearly 100% extension of the ν 2 data.

Analysis of the ν8 band of methylene fluoride

Abstract The high resolution infrared absorption spectrum of the ν 8 band of methylene fluoride has been measured on a BOMEM DA 3.002 Fourier transform spectrometer in the region 1400–1465 cm −1 . More than 900 transitions have been assigned in this A -type band centered at 1435.6355 cm −1 . The data have been combined with the upper state microwave measurements in a weighted least-squares fit to obtain molecular constants for the upper state resulting in an overall standard deviation of 0.0004 cm −1 .

High-resolution FTIR study of the ν4 band of CH2F2

Abstract The infrared absorption spectrum of the ν 4 fundamental band of CH 2 F 2 has been measured in the region 460–600 cm −1 under high resolution. More than 2700 lines have been assigned in this B -type band of the lowest fundamental centered at 528.5 cm −1 . These data have been combined with all available pure rotational measurements on the upper state in a least-squares fit. Accurate values for the band origin and other molecular parameters for the ν 4 state have been obtained which fit the data with an overall standard deviation of 3.7 × 10 −4 cm −1 .

Intensities of lines in the bands ν2 and ν4 and the transition dipole moments of PH3

Abstract The absolute intensities of 57 vibration-rotational spectral lines of transitions to the vibrational states v 2 = 1 and v 4 = 1 of PH 3 have been measured with a diode laser. With account being taken of the mixing of the wavefunctions of both vibrational states, the values of the vibrational transition moments and their relative signs were determined by a least-squares fit to the experimental data: 〈0, 0 0 ∥ μ z ∥1, 0 0 〉 = (0.23913 ± 0.00093) × 10 −30 C m and 〈0, 0 0 ∥ μ x ∥0, 1 ±1 〉 = −(0.14060 ± 0.00137) × 10 −30 C m.

Raman and i.r. studies of the antileprotic drug Dapsone

Abstract No information is available on the mode of action of Dapsone in leprosy treatment, the phenomena of drug resistance and toxicity. Information on the interaction of Dapsone with serum proteins can be obtained at the molecular level by spectroscopic investigations on structural changes of the system. As a first step in these investigations, the i.r. and laser Raman spectra of Dapsone and N-deutero Dapsone have been obtained. The characteristic vibrational frequencies of the NH2 group, the SO2 group and the aromatic ring have been identified and assigned from isotope shifts and studies in various solvents.