S. Ghersetti

Infrared bands of 12C2HD

Abstract The rotational structure of about 40 bands of 12C2HD observed in the region 6000−600 cm−1 has been measured and interpreted with the purpose of determining a comprehensive set of molecular constants for this isotopic variety of acetylene. Combining these data with the results for 12C2H2 and 12C2D2, a reevaluation of the equilibrium internuclear distances for the acetylene molecule has been made: r e (CH) = 1.06215 ± 17 × 10 −5 A and r e (CC) = 1.20257 ± 9 × 10 −5 A were obtained. This paper presents all the molecular constants derived in this study.

Interpretation of the acetylene spectrum at 1.5 μm

Abstract Bands of acetylene in the region 6680-6460 cm −1 recorded with a high resolution infrared spectrograph are assigned to transitions and molecular constants of the levels involved have been evaluated.

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.

Infrared absorption studies in the vapor phase of CF3Br: Spectra between 1800 and 400 cm−1

Abstract An extensive investigation of the ir spectrum in the gas phase of CF 3 Br was made under medium resolution in the range 1800 to 400 cm −1 . The results of this study enabled an unambiguous and self-consistent assignment of a high number of fundamentals, overtones, combinations, and “hot” bands absorbing in different regions to be made. The vibrational origin of the low-lying ν 3 fundamental was evaluated by applying the Ritz Combination Principle; for bands where this mode is somehow involved the 79 81 Br isotopic shift was observed. Molecular parameters obtained from the rotational structure of the perpendiculars ν 5 and ν 2 + ν 5 are also presented.

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 Spectra of Benzophenone and Its p-Halogen Derivatives

Abstract Although the vibrational spectrum of benzophenone has been analysed to some extent (1,2), and an attempt to calculate the normal vibrations was also made (3), a full systematization of the fundamentals of this molecule is not reached yet.

A vibrational analysis of the gas phase i.r. spectrum of CHFCl2

Abstract The gas-phase i.r. spectrum of natural CHFCl2 was recorded under moderate resolution and a number of regions between 3100 and 350 cm−1 were analysed. All the fundamentals but ν6 (lying at 277 cm−1) were observed and characterized; the band centre of the latter was evaluated by difference of suitable vibrational levels. Numerous combinations, ‘hot’ and ‘difference’ bands were assigned. The chlorine isotopic splitting pattern, often originating from a complex spectral structure, was also interpreted by the support of a normal coordinate analysis. Examples of possible Fermi resonance interactions were considered.

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.

Infrared laser spectroscopy and rovibrational analysis of the ν5 fundamental of cis-1-chloro-2-fluoroethylene

The infrared spectrum of cis-1-chloro-2-fluoroethylene (cis-CHClCHF) has been investigated in the ν5 band region between 1220 and 1250 cm−1, at a resolution of about 0.002 cm−1, using a tunable diode laser spectrometer. This fundamental of symmetry species A′ yields a strong a/b-hybrid band with contributions of comparable intensity from both the components. The rovibrational analysis led to the identification of 3800 lines (J⩽69, Ka⩽25) for the ν5 band of 35Cl species, whose origin is at 1231.849 cm−1. Using Watsons A-reduction Hamiltonian in the Ir representation, a set of spectroscopic parameters up to sextic centrifugal distortion terms was obtained for the v5=1 state, which turned out to be free from perturbations.