R. Visinoni

Infrared studies of acetophenone and its deuterated derivatives

Abstract The i.r. spectra of acetophenone and their deuterated analogues (- d 3 , - d 5 , - d 8 ) in the liquid-phase have been recorded and analyzed in the range 4000-130 cm −1 . Additional data on band contours in the gas-phase, in conjunction with the deuteration effects, allowed us to assign all the fundamentals for the four isotopic varieties. A valence force field calculation was also used to support the proposed assignment.

Diode laser spectra of the ν1 band of CF335Cl

Abstract The vibration-rotation spectrum of the ν 1 fundamental of CF 3 Cl, with natural isotopic abundance, has been recorded in the 1099 to 1116 cm −1 region using a tunable diode laser spectrometer. A majority of the measurements has been made by keeping the sample at low temperature (≈200°K) in order to avoid the strong interference arising from “hot” band absorptions. The K structure of many P ( J ) and R ( J ) multiplets as well as the individual lines of the Q branch of CF 3 35 Cl isotopic species have been positively identified; the assignment of rotational transitions has been extended up to J = 40. A weak perturbation affecting the rotational levels with K = 18 and J ′ ≥ 28 has also been observed. More than 1000 P , Q , and R transitions have been used for the least-squares fit to the energy expression including the quartic centrifugal distance coefficients. Molecular constants have been evaluated for the ν 1 band of CF 3 35 Cl.

Vapor phase infrared spectrum of CF3Cl in the region 4.8–16 μm☆

Abstract The gas phase infrared spectrum of CF 3 Cl was studied at medium resolution in the range 2100-600 cm −1 . A high number of bands including fundamental, overtone, combination, and “hot” bands of the two species, CF 3 35 Cl and CF 3 37 Cl, with natural isotopic abundance, was identified. The frequency values of the two long-wavelength fundamentals, ν 3 and ν 6 , were evaluated with higher accuracy by differences of suitable combination and “hot” bands. The Q -branch rotational structure of the ν 2 + ν 5 perpendicular band for the main variety was analyzed and the molecular constants obtained are reported.

Infrared laser spectrum of cis-CHCl=CHF near 1060 cm-1: rovibrational analysis of the perturbed v6 fundamental and determination of the constants of the dark vibrational state v9+v10

Cis-1-chloro-2-fluoroethylene has been synthesized, and the gas-phase infrared spectrum has been investigated in the ν6 band region around 1060 cm−1, at Doppler-limited resolution, using a tunable diode laser spectrometer. This fundamental of symmetry species A′ presents an a/b-hybrid band with contributions from both the components. The rovibrational analysis led to the identification of more than 2000 transitions (J ≤ 84, Ka ≤ 19) for the ν6 band of the 35C1 species, whose origin is at 1062.224cm−1. Different excited state perturbations occur throughout the band, caused by the first-order b-type Coriolis resonance with the ν9 + ν10 vibrational state. Using Watsons A-reduction Hamiltonian in the I r representation, a set of spectroscopic constants for both the upper states ν6 and ν9 + ν10 has been obtained. Parameters for the perturber were determined from the interaction effects near the observed crossings in the ν6 band, using a dyad model including first-order b-type Coriolis interaction.

High-resolution infrared study of the 2ν50 band of CF3Cl

Abstract The vibration-rotation spectrum of the 2 ν 5 0 band of CF 3 Cl, with natural isotopic abundance, has been investigated using a tunable diode laser spectrometer. The measurements have been performed at low temperature (∼200 K) in order to minimize the congestion of the “hot” bands. The K structure was resolved and identified; the assignment of rotational transitions has been extended in the R branch up to J = 49 and 48 for CF 3 35 Cl and CF 3 37 Cl, respectively. The low- K values of the main isotopic species were found to be rotationally perturbed and the interaction mechanisms have been interpreted on the basis of l (2, 2) and l (2, −1) resonances between 2 ν 5 0 and 2 ν 5 ±2 . Excited state parameters up to quartic terms have been determined for both isotopic varieties.

Infrared study of the ν5 fundamental of CF2HCl by FTIR spectroscopy

Abstract The infrared spectrum of natural CF 2 HCl has been investigated in the ν 5 region at a resolution of ca. 0.004 cm −1 using a Fourier transform infrared spectrometer. The ν 5 fundamental, which can be approximately described as a CF 2 deformation mode, gives rise to an a c hybrid band. The rovibrational analysis has been carried out in the P and R branches, and more than 1000 lines belonging to CF 2 H 35 Cl have been assigned. Transitions with K ′ a ≤ 6, J ′ up to 48 ( a -type) and K ′ e ≤ 11, J ′ up to 33 ( c -type) have been identified in the region investigated. From the assigned transitions a set of spectroscopic constants using Watsons A -reduction Hamiltonian has been derived for CF 2 H 35 Cl ν 5 band. Simulations in the Q -branch region enabled us to establish the character of the hybrid band which was determined to be composed of about 30% of a and 70% of c components.

Diode laser spectrum of CF3Cl in the region of 1120 cm−1

Abstract The gas-phase infrared spectrum of CF3Cl, with natural isotopic abundance, has been investigated in the ν1 region near 1120 cm−1 using a tunable diode laser spectrometer. The measurements have been carried out by keeping the sample at low temperature (∼200 K) to minimize the strong interference arising from “hot” band transitions. The K structure of many R(J,K) clusters belonging to the ν1 fundamental of CF335Cl (J = 41–65) and CF337Cl (J = 45–67) has been resolved and unambiguously identified. About 500 and 150 lines for CF335Cl and CF337Cl, respectively, have been analyzed by a least-squares procedure and spectroscopic parameters up to the sextic terms have been determined for both isotopomers. Additionally, for the CF335Cl species a weak Δl = Δk = ±2 type interaction of ν1 with 2ν5±2, no line of which has been observed, occurs locally for K = 18–21 rotational levels.

High-resolution infrared spectrum and analysis of the ν1 band of CF337Cl

Abstract The rotational structure of CF 3 37 Cl ν 1 band has been investigated using spectra of trifluorochloromethane in natural isotopic abundance, recorded with a tunable diode laser spectrometer. The spectra analyzed have been obtained by keeping the sample at low temperature (∼200 K) to minimize the strong interference arising from “hot” band transitions. The K structure of many P(J) and R(J) multiplets has been resolved and positively identified: the maximum J value reached in the P and R branches was 38 and 40, respectively. About 650 unblended lines have been used for the least-squares fit to the energy expression including the quartic centrifugal distortion coefficients. Molecular constants for the ν 1 band of CF 3 37 Cl have been derived. A weak perturbation affecting the rotational levels with K = 18 and J ′ ≥ 36 has also been observed.

Analysis of the ν1 band of trifluorobromomethane by diode laser spectroscopy

Abstract The vibration-rotation spectrum of the ν 1 band of CF 3 Br, with natural isotopic abundance, has been investigated by means of a tunable diode laser spectrometer. The measurements have been performed by keeping the sample at low temperature (∼200 K) in order to minimize the strong interferences due to “hot” band absorptions. The fine structure of many P ( J ) and R ( J ) clusters has been resolved and analyzed. The assignment of rotational transitions has been extended up to K = 24 and J = 51 and 50 for CF 3 79 Br and CF 3 81 Br, respectively. A total of 344 (CF 3 79 Br) and 433 (CF 3 81 Br) unblended lines were used in a least-squares fit to the energy expression up to the quartic coefficients, σ ( J , K ) ≅ 8 × 10 −4 cm −1 , and molecular parameters for the ν 1 fundamental of both isotopomers were determined.

High-resolution FTIR spectrum of the ν5 band of 1,1-difluoroethylene around 550 cm−1

Abstract The infrared spectrum of CF 2 CH 2 recorded in the range 400–4000 cm −1 with a Fourier transform infrared spectrometer has been studied in the ν 5 region. This fundamental approximately described as a CF 2 scissor mode gives rise to an a -type band showing in most regions of the spectrum distinct patterns characteristic of molecules approaching the oblate symmetric top limit. The rovibrational analysis extended to the P , Q , and R branches led to the identification of about 3000 transitions covering J and K a values up to 70 and 46, respectively. Using Watsons A -reduction Hamiltonian the assigned transitions provided a set of accurate rotational and centrifugal distortion constants for the first excited vibrational state of the ν 5 band of CF 2 CH 2 .