A. Scalabrin

The infrared absorption spectra and normal coordinate analysis of 13CH3OH, 13CD3OH, and 13CD3OD

Abstract The infrared absorption spectra of the gas-phase 13C-methanol isotopomers, 13CH3OH, 13CD3OH, and 13CD3OD, were measured in the wavenumber region between 400 and 4000 cm−1, at instrumental resolutions of 4 and 0.12 cm−1. The fundamental vibrational wavenumbers were assigned from the spectra with the aid of a normal coordinate analysis using the valence force constants recently determined for the gas-phase 12C isotopomers. Using the fundamental wavenumbers of both 12C and 13C-methanol isotopomers, we obtained a new set of force constants for the methanol molecule by a simultaneous least-squares adjustment to a total of 67 observed wavenumbers.

New FIR laser lines from CD3OD optically pumped by a CO2 waveguide laser

In this work we report new FIR laser lines from CD3OD optically pumped by a CO2 waveguide laser. The wide tunability of this laser (290 MHz) makes it possible to pump absorption lines with large frequency offset relative to the CO2 laser line center, which are not possible by using conventional CO2 lasers. As a consequence 19 new laser lines have been discovered, ranging from 38.0 μm to 455.2 μm in wavelength. For all lines, precise frequency offset measurements between the CO2 line center and the center of the absorber CD3OD line were performed using the transferred Lamb-dip technique. We also present direct Doppler-free offset measurements of infrared absorption, obtained within the FIR laser cavity itself, using optoacoustic detection.

Measurement and assignment of new FIR laser lines in12CH3OH and13CH3OH

We have found twelve new FIR laser lines in12CH3OH and thirty three in13CH3OH. Both molecules were pumped by a regular cw CO2 laser. We have also assigned 2013CH3OH laser lines to specific rotational energy levels in the excited C-O stretchhindered rotation combined states

IR and FIR spectroscopy of 13CD3OH around the 10P(22) and 10P(24) CO2 laser lines: New FIR laser emissions, frequency measurements and assignments

By using high resolution infrared Fourier transform data on 13CD3OH and the 10P(22) and 10P(24) lines of a waveguide CO2 laser to optically pump this methanol isotope, eight new FIR laser lines were observed. The frequencies of five laser lines were directly measured by heterodyne detection with already known laser lines. Particularly interesting are the lines pumped by the 10P(24) line, since a triade of emissions could be completely assigned.

Spectroscopy of the excited C-O stretching Q branch of 13CD3OH: Measurement and assignment of new FIR laser lines

Abstract The Q branch of the C-O stretching fundamental band of 13CD3OH has been investigated. Starting from a high resolution (4 × 10−3cm−1) infrared Fourier transform spectrum and using a waveguide CO2 laser of 300 MHz tunability and an acoustooptic modulator for an extension of ±90 MHz, 31 new FIR laser lines have been observed. The related absorptions have been measured by means of optoacoustic detection. The frequency of one new FIR laser line was also measured. Eight tentative assignments are proposed for the IR absorption and FIR laser emissions.

New FIR laser lines from CHD2OH optically pumped by a cw CO2 laser

This work reports 83 new optically pumped far infrared laser lines, using deuterated methyl alcohol, CHD2OH, as active medium. For each line we list the measured wavelength, its polarization relative to the pump line, the optimum gas pressure and the CO2 laser pump power at the maximum absorption.

CHD/sub 2/OH optically pumped by a waveguide CO/sub 2/ laser: new far-infrared laser lines from the CD/sub 2/ wagging vibrational mode

For the first time, a wide tunability waveguide CO/sub 2/ laser was used to pump the CHD/sub 2/OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD/sub 2/ wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements.

Optically pumped /sup 13/CD/sub 3/OH: far infrared laser lines and assignment

Fourier transform and IR optoacoustic absorption data of /sup 13/CD/sub 3/OH were used to search for new FIR laser lines. We have used a waveguide CO/sub 2/ laser of 300 MHz tunability as the optical pumping source. We report the observation and characterization of 13 new lines. Three of these lines are associated with absorbing transitions appertaining to the weak /sup 13/CD/sub 3/ asymmetric bending mode. >

Laser spectroscopy of calcium in hollow-cathode discharges

We investigated the use of hollow-cathode discharges for high-resolution and high-sensitivity spectroscopy, using atomic calcium. Spectra with sub-Doppler resolution of Cai transitions at 423 (resonant), 610, 612, 616, 645, 657 (intercombination), and 672 nm were obtained by optogalvanic saturation spectroscopy in lamps filled with argon (0.6 and 2.5 Torr) and krypton (0.6 Torr). A Doppler background that is due to velocity-changing collisions, which may severely limit the resolution, can be greatly reduced by the choice of buffer gas. Sub-Doppler linewidths comparable with those achieved in atomic beams have been obtained, making a properly chosen hollow-cathode lamp a convenient tool for high-resolution spectroscopic experiments, providing wavelength references for laser frequency tuning. The sensitivity of optogalvanic detection and the excitation of most electronic levels by the discharge make these lamps attractive also for investigating weak and excited level transitions with the use of a simple experimental setup.

Frequency measurements of optically pumped far-infrared laser lines

In this work, we report the frequency measurements of optically pumped far-infrared (FIR) laser lines. We use the heterodyne technique of mixing FIR laser radiation and microwave radiation on a metal-insulator-metal (MIM) point contact tunnel diode, to determine the FIR laser frequencies. The two FIR laser systems, consisting of CO/sub 2/ waveguide pump lasers and Fabry-Perot FIR laser cavities, and MIM diode were developed by us. To check the system, we have measured some FIR laser line frequencies previously reported in the literature. An average fractional frequency reproducibility of /spl plusmn/7/spl times/10/sup -7/, between our measurements and the previous ones, permit us to use our system to measure five new FIR laser frequencies. >