High‐Resolution Fourier Transform Infrared Spectroscopy

Abstract

Recent developments and applications of high‐resolution Fourier transform spectroscopy are reviewed. A short historical summary of the development of high‐resolution interferometric Fourier transform infrared (FTIR) spectrometers is given and the possibilities of the currently most highly resolving FTIR spectrometers, including a current prototype built for the Zürich group at the Swiss Light Source SLS as a synchrotron light source, are discussed. A short description of the principles of FTIR spectroscopy is given and the resolution of current spectrometers is illustrated by FTIR spectra of CO, CO 2 OCS, N 2 O, CS 2 , and CH 4 and its isotopomers. The computational tools necessary to analyze FTIR spectra are described briefly. As examples of rovibrational analysis of more complex spectra, selected molecules CHCl 2 F, CDBrClF, pyridine (C 6 H 5 N) and pyrimidine (C 4 H 4 N 2 ), and naphthalene (C 10 H 8 ) are discussed. The spectrum of CHCl 2 F, a fluorochlorocarbon, is of interest for a better understanding of the chemistry of the Earth's atmosphere. It also possesses an isotopically chiral isotopomer CH 35 Cl 37 ClF analyzed in natural abundance. CDBrClF is a chiral molecule and therefore the analysis of its rovibrational spectra provides the basis for carrying out further experiments toward the detection of molecular parity violation. The analyses of the pyridine, pyrimidine, and naphthalene FTIR spectra illustrate the potential of the new generation of FTIR spectrometers in the study of spectra and rovibrational dynamics of aromatic systems and molecules of potential biological interest. In particular, naphthalene is a prototype molecule useful in gaining an understanding of the unidentified infrared bands (UIBs) detected in several interstellar objects.

Molecular Quantum Mechanics and Molecular Spectra, Molecular Symmetry, and Interaction of Matter with Radiation

“…Another spectroscopic technique which relies on Fourier transformations is interferometric Fourier-transform spectroscopy, which is related, but not identical to time-resolved spectroscopy. The principles and applications of interferometric Fourier-transform spectroscopy are described in Albert et al (2010).…”

“…When one has a true intramolecular process leading to a homogeneous Lorentzian line shape combined with inhomogeneous Doppler line shape one finds a shape from convolution of the two functions, a Voigt line shape (see Albert et al (2010)). Sometimes, with very good data, the individual homogenous and inhomogeneous contributions can be separately evaluated (see for instance Hippler et al (2007) for an example).…”

“…If the Lorentzian line shape results from a bimolecular (pseudo first order) process by collisions with a heat bath (see Albert et al (2010)), then the collisional broadening line shape cannot be simply convoluted with the Doppler shape, but one can have many complex effects such as Dicke narrowing, line mixing and shifting, etc.…”

Synchrotron-based highest resolution FTIR spectroscopy of chlorobenzene

“…The use of synchrotron radiation sources has greatly enhanced the possibilities of highest resolution Fourier Transform Infrared spectroscopy of polyatomic molecules [1][2][3][4][5][6][7][8][9][10][11]. In recent work we have shown that the infrared spectra of molecules as complex as naphthalene [3], azulene [8] and indene [10] can be rotationally resolved and analyzed, which can help the search for the spectra of such molecules in an astrophysical context.…”

Optical fiber interferometer array for scanless Fourier-transform spectroscopy

“…In an FT spectrometer, the intensity variation of the output beam is measured while scanning an interferometer delay line whose longest optical path determines the spectral resolution of the device, with the latest developments [4] reaching a resolution limit of 0.0005 cm −1 as a result of an optical delay of 11.7 m. Resolutions up to 100 kHz have also been demonstrated with frequency comb FT spectrometers [5]. FT spectrometers benefit from a large radiant throughput (étendue), which is an intrinsic property of a Michelson interferometer [6,7] and can be readily combined with extreme laser sources of petawatt-power ultrashort pulses [8], allowing a precise characterization of chemical compounds that could shed light on some current astrophysical problems [9,10].…”