João Carlos Silos Moraes

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.

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.

CD3OD optically pumped by a wave guide CO2 laser: New FIR laser lines and frequency measurements

Abstract We report the discovery of new FIR laser lines from the CD 3 OD molecule optically pumped by a waveguide CO 2 laser. The increased tunability (300 MHz) with respect to a conventional CO 2 laser permits pumping IR CD 3 OD lines of larger offset. As a consequence 19 new laser lines have been discovered and the known FIR laser lines from this important molecule are thus increased to 220. For all observed laser lines, precise offset measurements of the pump lines from the CO 2 laser were performed through the transferred Lamb-Dip technique. The frequency of seven laser lines was also directly measured by heterodyne detection with already known laser lines. An additional new FIR laser line was found to be generated by the CD 3 OH molecule.

Diode laser and Fourier transform spectroscopy of the13CH3OH C-O stretching mode

In this work we present high resolution Doppler limited absorption spectra measurements of the C-O stretching mode of13CH3OH, obtained from diode laser spectroscopy, and the Fourier Transform spectrum obtained at 0.12 cm−1 resolution. By using these data and previously known spectroscopic information, we determined the frequency and the J quantum number for the multiplets of the P and R(J) branches of the C-O stretching fundamental band. Infrared transitions in coincidence with emission lines of the regular CO2 laser and some of its isotope parents are pointed out.

Experimental investigation of13CD3OH infrared transitions by means of optoacoustic spectroscopy

A systematic investigation of13CD3OH infrared transitions around CO2 laser line emissions is performed by means of optoacoustic detection. Using a waveguide CO2 laser of 290 MHz tunability and, in some cases, an acoustooptic modulator to provide an extension of 180 MHz, 108 transitions are observed. Measurements of pump off-set and relative intensity have been performed. The data may be compared with those previously reported of high resolution Fourier Transform spectroscopy.

Vibrational and Rotational Spectroscopy of 13CD3OD

We have used Fourier Transform spectral data on the C-O stretching mode of 13CD3OD in order to perform a vibro-rotational analysis for this molecule. We have estimated a few molecular parameters of the ground and C-O stretching vibrational modes. Based on these parameters, and by using the Kwan-Dennison model, we propose assignments for a number of far-infrared laser transitions of 13CD3OD.

Doppler-free optoacoustic measurements in FIR laser active molecules

Abstract Saturation effects in FIR laser active molecules were observed by using a Doppler-free optoacoustic spectrometer. 13CH30H and CD3OH were firstly used to calibrate the optoacoustic spectrometer. Some new infrared transitions could be observed. By using a waveguide CO2 laser as optical source and CD3OD as the main absorption molecule we were able to observe 35 infrared transitions, several of which not previously reported. As a consequence, some of these transitions were used in an experiment of optical pumping to search for new FIR laser lines. The collisional broadening influence on the linewidth of Doppler-free optoacoustic signals was also observed.

Electric field effects on roto-vibrational transitions of13CD3OH1

We used a Stark-Optoacoustic cell and hybrid waveguide resonators to perform an Infrared and Far Infrared Stark Spectroscopy study on some transitions of13CD3OH. Different behaviours of the transitions in the presence of a d.c. electric field were observed. The Stark splittings of six FIR laser lines ranging from 34 to 136 MHz/kVcm−1 were determined. The analysis of the behaviour of the IR and FIR transitions in the presence of the external electric fields gives important and exclusive information on the levels involved in the transitions.

DCOOD Optically Pumped by a 13CO2 Laser: New Terahertz Laser Lines

In this work, we report new optically pumped terahertz laser lines from DCOOD. An isotopic 13CO2 laser was used for first time as pump source, and a Fabry–Perot open cavity was used as a terahertz laser resonator. Optoacoustic absorption spectra were used as a guide to search for new terahertz laser lines. We could observe six new laser lines in the range from 303.8 μm (0.987 THz) to 725.l μm (0.413 THz). The lines were characterized according to wavelength, relative polarization, relative intensity, and optimum working pressure. The transferred Lamb‐dip technique was used to measure the frequency absorption transition both for this laser lines.