1,720,978 research outputs found
AN AUTOMATED 2-CHANNEL WAVE-NUMBER CALIBRATION PROGRAM FOR A DIODE-LASER SYSTEM
No full textAn accurate and convenient two-channel wavenumber calibration program has been developed for a Laser Photonics diode laser system. The method is based solely on comparison of sample and reference spectra, as recorded and stored by the standard sweep control and data acquisition facilities supplied with the system. The calibration program reads the sample and reference data files in Laser Photonics format, extracts the spectral data, and converts them into standard IEEE data format. A simple procedure is implemented for peak finding, with the sample peak wavenumbers calculated from a calibration curve determined by least-squares fitting to the reference wavenumbers. Provided the reference spectrum has a suitable distribution of peaks, a calibration precision of +/-0.0002 cm-1 or better is obtained for nitrogen-cooled diodes over the full width of the diode laser scan, and from +/-0.0005 to +/-0.001 cm-1 for closed-cycle helium cooling, of the same order as the original standard reference data. Given the rapid ongoing improvement in availability of good reference spectra for all regions, this program offers a simple, reliable, and automatic procedure for accurate measurement of diode laser data. (C) 1994 Academic Press, Inc
CH3OH LASER LINE ASSIGNMENTS AND FREQUENCY PREDICTIONS
No full textBy utilizing the results of high resolution infrared (IR) and far-infrared (FIR) spectroscopy we discuss the reported assignments of more than 300 FIR laser lines in optically-pumped CH3OH. The analysis has been done both by feeding each IR-pump/FIR-laser transition system into the computer fit program described in previous works, and by combining the CO2 laser optical pumping frequency, the FIR laser frequencies and the IR and FIR spectroscopic measurements to construct closed frequency loops. When the energy balance of a loop is found to be zero to within experimental uncertainty the assignments of all sides of the loop are supported. In addition, improved accuracies by one to two orders of magnitude for the FIR laser frequencies, and predictions for new laser lines have been obtained for a number of systems from loop combination differences
High-resolution spectroscopy of (CH3OH)-O-18: Stark behavior of FIR laser lines
No full textWe report the Stark behavior of 31 FIR laser lines of (CH3OH)-O-18 optically pumped by a CO2 waveguide laser. We observe various behaviors for different laser lines: power decrease, power enhancement, shifting and splitting of the laser lines, or no effect at all. Since the observed Stark line shapes depend critically on the quantum numbers of the molecular levels involved in the laser cycle, we used the Stark effect to test many of the known assignments of FIR laser lines of (CH3OH)-O-18. Nineteen previous assignments were confirmed and a new one is proposed. Two new laser lines are also reported and characterized in wavelength, offset and polarization. The linear Stark shifts were calculated including both the usual first-order mu(a)-type terms and the mu(b)-type contributions arising from the mixing of Stark and molecular asymmetry terms. This second term is incorporated in the calculations by writing mu(n, tau, K, J) = mu(a)S(b)(n, tau, K J), where S-b(n, tau, K, J) is a state-dependent scaling factor close to unity. (C) 1996 Academic Press, Inc
INVESTIGATION OF THE GROUND VIBRATIONAL-STATE OF CD3OH BY A NEW RITZ PROGRAM FOR DIRECT ENERGY-LEVEL FITTING
No full textThe complete absorption spectrum of CD3OH between 30 and 1200 cm-1 has been measured on the Bruker Fourier transform spectrometer of the Physical Chemistry Institute of the University of Giessen. In the present work we present the assignment of more than 20 000 lines between 30 and 850 cm-1, corresponding to transitions within the vibrational ground state of the molecule. These assignments have been performed with the help of a new computer program which evaluates the energies of the involved levels by the Rydberg-Ritz combination principle and can tackle such perturbations as Fermi-type resonances or Coriolis interactions. Up to now this program has evaluated the energies of 1789 levels belonging to A-type symmetry and of 2417 levels belonging to E-type symmetry, all in the vibrational ground state of the molecule. The evaluation of the energy level values allows comparisons between different isotopic species. (C) 1994 Academic Press, Inc
(CH3OH)-O-18 - FIR LASER LINE FREQUENCY MEASUREMENTS AND ASSIGNMENTS
No full textObservations of far-infrared (FIR) laser emission and assignments of FIR laser lines have been reported in the literature for the O-18 isotopomer of methanol optically pumped by CO2 lasers. So far, wavelengths have been measured for 100 FIR laser lines, and assignments for 26 of these lines have been proposed. However, some assignments were uncertain, with several possible alternatives, notably for the lines pumped by the 10R(20) CO2 line. The present work combines new accurate FIR laser heterodyne frequency measurements with the results of Fourier transform spectroscopic studies of the CO-stretching and FIR torsion-rotation bands of CH3 18OH in a detailed analysis of the FIR laser emission. Precise frequencies have been determined for 22 of the laser lines, and five new laser lines have been observed. The spectroscopic results have led to unambiguous assignments for 20 of these lines and their confirmation through transition combination loops. The assignments of 13 of the lines are given for the first time. With the new results, the enigmatic 10R(20) situation has been almost completely resolved
Fourier transform synchrotron spectroscopy of torsional and CO-stretching bands of CH(3)(17)OH
No full textThe Fourier transform spectrum of the CH(3)(17)OH isotopologue of methanol has been recorded in the 65-1200 cm(-1) spectral region at a resolution of 0.00096 cm(-1) using synchrotron source radiation at the Canadian Light Source. Here we present an extension to higher torsional states of our investigation of the torsion-rotation transitions within the small-amplitude vibrational ground state, now including assignments of more than 16 500 lines involving quantum numbers in the ranges v(t) <= 3, J <= 30 and vertical bar K vertical bar <= 12, as well as a study of the strong CO-stretching band centered at 1020 cm(-1). Energy term values have been determined for assigned ground and CO-stretching levels by use of the Ritz program, and have been fitted to series expansions in powers of J(J + 1) to determine substate origins and effective B values. Several Fermi anharmonic and Coriolis level-crossing resonances coupling the CO stretch with high torsional ground-state levels have been identified and characterized. The study is motivated by astrophysical applications, with a principal aim being the compilation of an extensive set of energy term values to permit prediction of astronomically observable sub-millimetre transitions to within an uncertainty of a few MHz. (C) 2011 Elsevier Inc. All rights reserved
THE SPECTRUM OF CH3OH BETWEEN 200 AND 350 CM-1 - TORSIONAL TRANSITIONS AND EVIDENCE FOR STATE MIXINGS
No full textAPPLICATIONS OF HIGH-RESOLUTION SPECTROSCOPY TO THE IDENTIFICATION OF FAR-INFRARED LASER-EMISSION FROM OPTICALLY PUMPED 13CH3OH
No full text- …
