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     

A new efficient far-infrared optically pumped laser gas: CH3 18OH

The¹²CH₃ ¹⁸OH molecule has been investigated for new far-infrared laser lines by optically pumping it with a cw waveguide CO₂ laser. The larger tunability (318 MHz) with respect to a conventional CO₂ laser permits the pumping of many¹²CH₃ ¹⁸OH lines. As a consequence 100 new laser lines have been discovered, ranging from 34.6 m to 653.2 m in wavelength. The infrared spectrum of¹²CH₃ ¹⁸OH has been observed and all the fundamental vibration energies measured.     

Optically-Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CH3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new far-infrared laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically-pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2-m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Optically Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CD3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new FIR, far-infrared, laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2 m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Investigation of 13CH3OH methanol: new laser lines and assignments

We have reinvestigated ¹³CH₃OH as a source of far-infrared (FIR) laser emission using a CO₂ laser as a pumping source. Thirty new FIR laser lines in the range 36.5 μm to 202.6 μm were observed and characterized. Five of them have wavelengths between 36.5 and 75 μm and have sufficient intensity to be used in LMR spectroscopy. Using Fourier-transform spectroscopic data in the infrared (IR) and FIR regions we have determined the assignment for 10 FIR laser transitions and predict nine frequencies for laser lines which have yet to be observed. Received: 17 July 2000 / Published online: 6 December 2000     

CH<Subscript>3</Subscript>OH optically pumped by a <Superscript>13</Superscript>CO<Subscript>2</Subscript> laser: new laser lines and assignments

We report 12 new THz (far-infrared) laser lines from methanol (CH₃OH), ranging from 58.1 μm (5.2 THz) to 624.6 μm (0.5 THz). A ¹³CO₂ laser of wide tunability (110 MHz) has been used for optical pumping, allowing access to previously unexplored spectral regions. Optoacoustic absorption spectra were used as a guide to search for new THz laser lines, which have been characterized in wavelength, polarization, offset, relative intensity, and optimum operation pressure. For 20 laser lines previously observed, we have measured the absorption offset with respect to the ¹³CO₂ laser line center. PACS 33.20.Ea; 33.20.Vq; 33.80.-b     

New far-infrared laser lines from CH3Cl and CH3Br optically pumped with a continuously tunable high pressure CO2 laser

In this paper we report on the detection of new far-infrared laser lines from CH₃Cl and CH₃Br optically pumped with a continuously tunable high pressure CO₂ laser. We found 80 new lines for CH₃Cl and 9 new lines for CH₃Br in the frequency region between 16 cm^–1 and 41 cm^–1, all due to stimulated Raman scattering. For the Raman gain regions bandwidths up to about 700 MHz were found. We also observed high intensity short far-infrared laser pulses of durations in the nanosecond regime.Permanent address: Physics Department, State Pedagogical University, SU-119435 Moscow, USSR     

New large offset far-infrared laser lines from CD3OH

The CD₃OH molecule has been investigated for new far-infrared laser lines by optically pumping with a cw waveguide CO₂ laser. The increased tunability (300 MHz) with respect to a conventional CO₂ laser permits to pump many new CD₃OH lines. As a consequence 108 new laser lines have been discovered, ranging from 42.9 to 1155 m in wavelength. On some lines the effect of an electric Stark field has been investigated demonstrating a laser frequency tuning. The total number of known FIR laser lines from CD₃OH is increased to about 340 making this molecule the most prolific together with CH₃OH.     

Laser frequency measurements and spectroscopic assignments of optically pumped 13CH3OH

A three-laser heterodyne system was used to measure the frequencies of twelve optically pumped laser emissions from ¹³CH₃OH in the far-infrared (FIR) region. These emissions, ranging from 54 to 142 μm, are reported with fractional uncertainties up to ±2×10^-7 along with their polarization relative to the CO₂ pump. Using the 9P32 and 10R14 CO₂ lines, complete spectroscopic assignments for two laser systems were confirmed. Received: 31 May 2001 / Published online: 19 September 2001     

Discovery and frequency measurement of short-wavelength far-infrared laser emissions from optically pumped <Superscript>13</Superscript>CD<Subscript>3</Subscript>OH and CHD<Subscript>2</Subscript>OH

A three-laser heterodyne system was used to measure the frequencies of twelve previously observed far-infrared laser emissions from the partially deuterated methanol isotopologues ¹³CD₃OH and CHD₂OH. Two laser emissions, a 53.773 μm line from ¹³CD₃OH and a 74.939 μm line from CHD₂OH, have also been discovered and frequency measured. The CO₂ pump laser offset frequency was measured with respect to its center frequency for twenty-four FIR laser emissions from CH₃OH, ¹³CD₃OH and CHD₂OH. PACS 07.57.Hm; 42.55.Lt; 42.62.Eh     

Infrared and far-infrared spectroscopy of CH3OH: TeraHertz laser lines and assignments

We use a ¹³CO₂ laser as optical pumping source to search for new THz laser lines generated from ¹³CH₃OH. Nineteen new THz laser lines (also identified as far-infrared, FIR) ranging from 42.3 μm (7.1 THz) to 717.7 μm (0.42 THz) are reported. They are characterized in wavelength, offset, relative polarization, relative intensity, and optimum working pressure. We have assigned eight laser lines to specific rotational energy levels in the excited state associated with the C-O stretching mode.     

New submillimetre laser lines from CH3OD and CD3OD

Thirteen new submillimetre emission lines have been observed when pumping CH₃OD using isotopic CO₂ lasers, and fourteen when pumping CD₃OD. Three isotopic CO₂ lasers were used¹²C¹⁶O₂,¹²C¹⁸O₂, and¹³C¹⁶O₂. The new lines were observed in a Fabry-Perot resonator. The wavelength ranges observed were from 55 to 320 m for CH₃OD and from 66 to 531 m for CD₃OD. The polarisation of the submillimetre laser lines relative to the CO₂ pump line has also been determined.     

Stark effect in the CO2 laser-pumped CH3OH far-infrared laser as a technique for high-resolution infrared spectroscopy

The potential of the Stark effect as a method for assigning far-infrared emission lines observed in infrared laser-pumped lasers is examined. The technique is applied to previously unassigned lines in CO₂ laser-pumped CH₃OH. Seventeen lines are shown to form an interrelated pattern and on the basis of combination relations a set of energy levels is identified which is not predicted by current models for the vibrationally excited CH₃OH molecule.     

New fir laser lines and frequency measurements from optically pumped13CD3OH3

We report the discovery of 57 new fir laser lines from¹³CD₃OH molecule optically pumped by a waveguide CO₂ laser of 300 MHz tunability. For all lines, precise frequency offset measurements between the CO₂ line center and the center of the absorbing¹³CD₃OH line were performed using the transferred Lamb-Dip technique. We have also measured directly the frequency of seven FIR laser lines by heterodyning with already known laser lines. We present a complete list of all known laser lines (134) and frequency measurements (24) for this molecule.Work supported by CNPq, FAPESP, FAEP-Brasil, and CNR-Italia     

Far infrared laser lines produced by methanol and its isotopic species: A review

Methanol (CH₃OH) is considered today one of the most important active media for the generation of laser radiation in the far-infrared (FIR) spectral region. Together with ten of its other isotopic species, it is responsible for the major part of the laser lines generated by the optical pumping technique. Due to the extreme importance of those molecules as laser generators, we understood that there was a necessity of a comprehensive work which would include as much pratical information as possible about each line.Chang et al⁽¹⁾ early recognized methanol as a source of strong FIR laser lines. Since then, more than 100 papers were published containing information about new laser emission. Recently, Moruzzi et al⁽¹¹⁴⁾ presented a review of 575 lines produced by¹²CH₃OH. In the present paper, we have extended the review to the various isotopic modifications of this molecule (namely¹³CH₃OH, CD₃OH,¹³CD₃OH, CD₃OD,¹³CD₃OD, CH₃OD, CH ₃ ¹⁸ OH, CH₂DOH, CH₂DOD and CHD₂OH), a total of nearly 2000 lines with wavelengths ranging from 19µm to 3030µm.     

Stark effect on CH3OH and CH3F FIR lasers: Large frequency tuning and resolved structures

The operation of a cw FIR laser in the presence of a strong electric field is described. A hybrid metal-dielectric waveguide is used and the cavity length is scanned to study how the frequency and power of the laser depend on the field strength. The results have also been checked by heterodyning with a conventional reference laser. We report the results obtained for the 496 μm line of CH₃F and the 70.5 μm and 119 μm lines of CH₃OH. A large frequency tunability of almost ±40 MHz is obtained in the best case with power levels in the mW range. A very simple theoretical model accounts for the experimental results. We also report the appearance of a new FIR line at about 204 μm when CH₃OH is pumped by the 9 μmP(34) of CO₂ in the presence of an electric field larger than 1.2 KV/cm.     

Discovery and characterization of optically pumped far-infrared laser emissions using laser magnetic resonance spectroscopy

A laser magnetic resonance spectrometer has been used to discover and subsequently measure a far-infrared laser emission: the 166.6-micron line of CH₂F₂, optically pumped by the 9P24 CO₂ laser. By recording spectra for the NH radical, the frequency of this laser emission has been determined to be 1799950±13 MHz. Spectra for the NH radical were also recorded with two other far-infrared laser emissions: the 160.4-micron line of N₂H₄ (9P46 CO₂ pump) and the 328.6-micron line of ¹³CH₃OH (9P12 CO₂ pump). From the NH spectra, a discrepancy of 2.1 GHz with the previously measured laser frequency was identified for the 160.4-micron line. A three-laser heterodyne system was then used to remeasure the frequency to be 1868475.5±0.5 MHz. The NH spectra were also used to determine the frequency for the 328.6-micron line to be 912366±7 MHz, in agreement with the value previously calculated from the Rydberg–Ritz combination principle. PACS 07.57.Hm; 32.60.+i; 42.62.Eh     

Frequency measurements of far infrared12CH3OH laser lines

We have measured the frequencies of 12 known and 3 new submillimeter laser lines obtained by pumping¹²CH₃OH with a cw waveguide CO₂ laser in a Fabry-Perot far infrared resonator. We have also measured the relative polarization and the pumping CO₂ frequency offset for each line.Supported in part by a joint grant with the U.S. National Science Foundation # INT80-19014 and the Brazilian Conselho Nacional de Pesquisas (CNPq).Work of the U.S. Government; not subject to U.S. copyright.     

New laser lines from CHD2OH methanol deuterated isotope

Through the optical pump technique we have reinvestigated the CHD₂OH molecule as a source of far-infrared (FIR) laser lines using for the first time a CO₂ laser lasing on regular, hot, and sequence bands. As a consequence, we present here spectroscopic data of 16 new FIR laser transitions from this molecule. Furthermore, we also present a catalogue of all FIR laser lines generated from CHD₂OH. Received: 13 July 2001 / Revised version: 25 October 2001 / Published online: 14 May 2002     

13CH3OH and13CD3OH optically pumped fir laser: New large offset emission and optoacoustic spectroscopy

27 new, large offset, FIR laser lines from¹³CH₃OH and one from¹³CD₃OH have been discovered by pumping with a high tunability waveguide CW CO₂ laser. Optoacoustic measurements of isotopic methyl alcohol have also been performed and the pump offsets of the new and of previously known lines have been measured and checked. Frequency tunability by Stark effect has been observed for 6 strong lines. Some assignments are discussed.