1,720,998 research outputs found
RESOLUTION OF MULTIPLE OVERLAPPING LINES IN THE ANALYSIS OF MOLECULAR-SPECTRA
No full textWe discuss two approaches to the treatment of blended lines in a molecular absorption spectrum. This problem of blended lines is relatively frequent in the dense and complex far-infrared and infrared spectra of methanol. The first technique utilizes an interactive computer line-profile analysis routine to resolve the blended features, while the second more directly separates closely adjacent peaks in the spectrum by employing 2f lock-in detection. In principle, both techniques can be applied to any spectrum where line overlapping occurs and in most cases make overlapped lines separable for analysis with practically the same precision as that for isolated lines. (C) 1994 Academic Press, Inc
LaseRitz: Far-infrared laser line assignment and prediction by the Ritz combination principle, with application to methanol and hydrazine
No full textA "LaseRitz" program is described for the systematic assignment and prediction of far-infrared laser (FIRL) transitions for a given molecule, such as methanol or hydrazine, which can be generated by optical pumping with known laser lines. The input data set for the program consists of identified molecular energy levels in ground and excited vibrational states, as compiled by our Ritz assignment program from the analysis of infrared (IR) bands and the FIR ground state spectrum. The program scans the data set for appropriate IR matches with an input list of laser pump lines for CO2, N2O, etc., and generates an output table of all possible FIRL,lines consistent with the molecular selection rules and lying within a prescribed wavenumber range. Initial tests on CH3OH have led to three likely new FIRL assignments; for N2H4, assignments have been found for 14 new FIRL transition systems and verified for five others. Lists have been produced (deposited as supplementary data with the JMS archive reached at www.idealibrary.com or available on request from the authors) of CH3OH and N2H4 FIRL lines potentially accessible by optical pumping with regular, sequence-band, hot-band, and isotopic CO2 lines, plus N2O lines for N2H4. The systematic approach with the LaseRitz program is more global and rigorous than earlier line-by-line studies, permitting calculation of all FIRL wavenumbers to spectroscopic accuracy. (C) 2000 Academic Press
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
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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Re-investigation of optically pumped hydrazine far-infrared laser around mu m from the 10HP and 10P bands of a pulsed CO2 laser: New lines and assignments RID D-2909-2009
No full textA high-peak-power (several hundreds of watts) pulsed CO2 laser, recently developed in our laboratory, has been used for exciting optically pumped far-infrared laser transitions of N2H4. A systematic search for N2H4 absorption coincidences with 10P and 10HP CO2 laser emissions has led to the observation of 27 new far-infrared laser lines, excited by 18 different absorption transitions. All of these new lines have been characterized in wavelength, offset, relative polarization, optimum operation pressure and intensity. Using the LaseRitz program, ten of these lines were assigned, corresponding to five laser systems. For other two laser systems possible J and K quantum numbers of the energy levels involved in the laser transitions were given
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Torsion-rotation global analysis and database for the (CH3OH)-O-18 isotopomer of methanol
No full textFourier-transform far-infrared spectra of (CH3OH)-O-18 in the 15-470 cm(-1) region have been analyzed by means of the Ritz assignment program. The far-infrared data have been combined with the literature microwave and millimeter-wave measurements in a full global fitting of the first three torsional states (v(t) = 0, 1, and 2) of the (CH3OH)-O-18 ground vibrational state. The fitted dataset includes 550 microwave and millimeter-wave lines and more than 17 000 Fourier-transform transitions covering the quantum number ranges J <= 30, K <= 15, and v(t) <= 2. With incorporation of 79 adjustable parameters, the global fit achieved convergence with an overall weighted standard deviation of 1.072, essentially to within the assigned measurement uncertainties of +/- 50 kHz for almost all of the microwave and millimeter-wave lines and +/- 6 MHz (0.0002 cm(-1)) to +/- 15 MHz (0.0005 cm(-1)) for the Fourier-transform far-infrared measurements. Based on the global fit results, a database has been compiled containing transition frequencies, quantum numbers, lower state energies and transition strengths. This database will provide support for present and future astronomical studies, such as the on-going Orion surveys in preparation for the launch of the Herschel Space Observatory, in identifying isotopic methanol contributions to interstellar spectra. (c) 2007 Elsevier Inc. All rights reserved
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