Seven rovibrational transitions of the (01(1)0) <-- (00(0)0) fundamental bending band of C3 have been measured with high precision with the use of a tunable far-infrared laser spectrometer. The C3 molecules were produced by laser vaporization of a graphite rod and cooled in a supersonic expansion. The astrophysically important nu 2 fundamental frequency is determined to be 63.416529(40) cm-1. These measurements provide the basis for studies of C3 in the interstellar medium with far-infrared astronomy.
Articles you may be interested inFar-infrared laser vibration-rotation-tunneling spectroscopy of water clusters in the librational band region of liquid waterThe farinfrared vibration-rotation-tunneling spectrum of the water tetramerd8Farinfrared laser vibration-rotation-tunneling spectroscopy of the propane-water complex: Torsional dynamics of the hydrogen bond.Thirteen vibration-rotation-tunneling (VRT) bands of the CH 4 -H 2 0 complex have been measured in the range from 18 to 35.5 cm-I using tunable far infrared laser spectroscopy. The ground state has an average center of mass separation of 3.70 A and a stretching force constant of 1.52 N/m, indicating that this complex is more strongly bound than Ar-H 2 0. The eigenvalue spectrum has been calculated with a variational procedure using a spherical expansion of a site-site ab initio intermolecular potential energy surface [J. Chern. Phys. 93, 7808 (1991)]. The computed eigenvalues exhibit a similar pattern to the observed spectra but are not in quantitative agreement. These observations suggest that both monomers undergo nearly free internal rotation within the complex.
Fifty-six transitions from the K=1 lower→K=2 lower tunneling–rotation band of water dimer have been measured and assigned at 22 cm−1 by direct absorption spectroscopy in a cw planar supersonic jet expansion using a tunable far infrared laser spectrometer. Two different models were used to fit the data and several spectroscopic constants were determined for the upper and lower states. This work supports the local IAM model recently proposed by Coudert and Hougen for the hydrogen bond tunneling dynamics of the water dimer. This model includes four different tunneling motions, all of which contribute to the observed tunneling splittings. This is the most complicated hydrogen bonded system considered to be well understood at this time, at least in the lowest few K states.
A detailed description is presented for a tunable far infrared laser spectrometer based on frequency mixing of an optically pumped molecular gas laser with tunable microwave radiation in a Schottky point contact diode. The system has been operated on over 30 laser lines in the range 10-100 cm-i and exhibits a maximum absorption sensitivity near one part in 106. Each laser line can be tuned by f 110 GHz with first-order sidebands. Applications of this instrument are detailed in the preceding paper. THE BERKELEY TUNABLE FAR-INFRARED LASER SPECTROMETERA. General description Tunable far-infrared (FIR) lasers have become powerful tools for investigating the structures of ions, radicals, and clusters, and for probing intermolecular forces through measurement of FIR spectra of van der Waals complexes. In the preceding paper we have described the rapid evolution of FIR laser spectroscopy and some recent applications. In this article we present a detailed description of the tunable FIR laser spectrometers currently used at Berkeley. We begin with a relatively general overview of the design, and then proceed to the details of construction and operation. It is our hope that this article will serve as a useful guide to those who seek to construct similar systems.The design of the tunable FIR laser systems used at Berkeley is similar to that of Farhoomand et al. ' In the following, we first present a general description of this design, in sufficient detail to afford all readers a reasonable understanding of the underlying principles and function. We then proceed to describe each component of the system in sufficient detail to effectively guide those actually seeking to construct a similar apparatus.The overall experimental design is diagrammed in Fig. 1. The complete spectrometer is built on a 5 ft. x 12 ft. vibration isolation honeycomb table. A COz. laser provides an intense mid-infrared beam (maximum power > 150 W) that is used to pump a molecular gas FIR laser. The CO2 laser is line tunable over some 100 different vibrationrotation transitions between 9.1 and 11 .O pm using a precision grating in first-order autocollimation. The output frequency is fine-tuned over the 65 MHz free spectral range of the cavity (limited by its 2.3 m length) using a piezoelectric transducer (PZT), and the zeroth-order beam reflected from the grating is focused into a CO2 spectrum analyzer to identify the laser line.The FIR laser is pumped coaxially by the COz laser beam, which circulates between the FIR laser end mirrors after expanding through a 4 mm hole in the input coupler. The 2.5 m cavity of the FIR laser is of the dielectric waveguide design, with planar gold-coated copper end mirrors. FIR power is coupled out through a lo-mm-diam hole in the end mirror, which is backed by a hybrid quartz/ dielectric mirror to reflect the pump beam, while transmitting the FIR output. The output beam of the FIR laser then enters a Martin-Puplett polarizing diplexer, which couples the laser radiation onto the (Schottky diode) comer cube mixer, while s...
The state of the art in far infrared (FIR) spectroscopy is reviewed. The development of tunable, coherent FIR radiation sources is discussed. Applications of tunable FIR laser spectrometers for measurement of rotational spectra and dipole moments of molecular ions and free radicals, vibration-rotation-tunneling (VRT) spectra of weakly bound complexes, and vibration-rotation spectra of linear carbon clusters are presented. A detailed description of the Berkeley tunable FIR laser spectrometers is presented in the following article.
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