Identification and prediction of optically pumped laser lines in ozone

Three previously observed optically pumped submillimeter laser lines are shown to be pure rotational transitions in the v₃ = 1 vibrational level of ozone. Using other anticipated coincidences between CO₂ laser lines and ozone absorption lines, a number of optically pumped laser transitions are predicted.     

IR absorption measurements and new FIR emission lines in CH3OH by use of a frequency-tunable CW waveguide CO2 laser

The IR absorption in CH₃OH in the vicinity of CO₂ laser lines has been measured quantitatively by use of a 300 MHz tunable waveguide CO₂ laser with output powers of about 3 W. Information on frequency offsets from the CO₂ line centers, small signal and saturated absorption coefficients of FIR laser pump transitions is obtained. Some stronger pump transitions with frequency offsets larger than 50 MHz gave rise to the observation of 8 new FIR emission lines with wavelengths from 43 to 125 μm.     

New N2O laser band in the 10 μm wavelength region

Fifty new laser lines have been observed in continuous emission from an N₂O laser by placing a hot N₂O absorber cell inside the laser cavity to suppress the regular laser lines. The new lines are identified as rotation-vibration transitions of the (00⁰2–10⁰1) band of N₂O.     

Laser-microwave double-resonance spectroscopy in CF3I with four CO2-laser lines

Double-resonance effects produced by three CO₂-laser lines, the 9.4-μmR(12),R(14), and R(18), have been newly observed. From an analysis of the observed laser-induced changes in intensity of various microwave transitions, the infrared transitions which were accidentally coincident with these three laser lines were determined. In every case an exact rotational assignment of the infrared transition was possible, but in some cases the assignment of the vibrational band involved was difficult. When the previously discussed (l) effects produced by the R(16) laser line are included these four consecutive laser lines pump a total of seven infrared transitions of CF₃I. It appears that all seven transitions belong to different fundamental, combination, and hot bands.     

Assignment of FIR Laser Lines of Hydrazine

With 228 known FIR laser emissions, hydrazine is the most prolific laser active molecules after methanol. But, due to the complexity of its rovibrational spectrum, only a few assignments of hydrizine FIR laser transitions are found in literature. Here we analyze 44 FIR laser lines of hydrazine excited by 20 different CO₂ pumps. The pump transitions are compared to available assignments of IR amino-wagging transitions. We propose values for the J and K quantum numbers involved in 41 FIR laser transitions, for 22 of them we give also the symmetry species.     

Resonant light absorption by the ordered structures of ions stored in a trap

Far-infrared laser action has been demonstrated in three previously unknown laser media. The substances used were: propargyl fluoride, 15-N cyanogen fluoride, and hydroxylamine. Assignments of the molecular transitions giving rise to the observed laser lines were made for the latter two compounds.New FIR laser lines were also observed with two substances, vinyl chloride and vinyl fluoride, which were already known as laser media by pumping with isotopic CO₂ and N₂O laser lines.The wavelengths of a total of 26 new FIR laser lines were determined together with the threshold pump power and an indication of the relative line strengths.     

New FIR lasers from CO2 laser-excited 1,1-difluoroethene

Forty two new far-infrared laser lines have been obtained from CH₂CF₂ by pumping with a 60 W CO₂ laser. Several of these emissions have been assigned to rotation transitions within the v4 and v9 vibration manifolds; hot and combination band transitions are suspected for the others.this work was funded by the Ministry of Defence     

Method for observing Doppler-free hot-band transitions

A novel spectroscopic method for highly sensitive detection of hot-band transitions based on infrared-infrared double resonance in a molecular beam was successfully demonstrated. The intensity of the infrared transitions from a vibrationally excited state is enhanced by two orders of magnitude by resonant laser pumping. The hot-band transitions are identified in connection with the assigned transitions in the fundamental band. Doppler-free spectral lines are observed. The experiment was carried out on the 2v ₃←v ₃ transitions of CH₃F with CO₂ laser pumping and probing.     

Infrared multi-line NH3 laser and its application for pumping an InSb laser

In this paper, infrared (IR) emissions from a TE CO₂ laser pumped NH₃ laser are reported. 38 IR laser lines were obtained from a CO₂ 9R(30) line pumped NH₃ : N₂ mixture by cooling a NH₃ laser tube, and 13 lines of them were new emission lines as far as we known. Four Q-branch lines were included and the others belonged to P-branch transitions. The 12.078 μm line, which was the strongest line in this experiment, was used to pump an InSb spin-fip Raman (SFR) laser which could be tuned from 13.35 to 13.55 μm.     

Optically pumped NH3 laser using a continuously tunable CO2 laser

The use of a continuously tunable CO₂ laser to optically pump the NH₃ laser via previously inaccessible absorption lines is described. Efficient laser action has thus been achieved in the 11–13 μm region on transitions formerly only obtained in buffered mixtures.     

FIR Stark spectroscopy on optically pumped CH3OH laser

An extensive theoretical and experimental analysis of the absorption and emission spectrum of a CH₃OH FIR-laser excited by a conventional CO₂ laser is presented. Particular interest is devoted to the Stark shifts of the pump and lasing lines and to the electric field dependence of the Fir-laser output of the various lines. The offsets with respect to the exciting radiation and the Stark shifts of the IR absorption (pump) lines are measured by means of the transferred Lamb dip technique. The theoretical behaviours of the Stark patterns are calculated for several choices of the quantum numbers and selection rules involved in the transitions. A large variety of experimental results are reported and compared to theory. Non-linear Stark shifts have been observed for the 37.5m FIR laser line and for the IR-pump transitions excited by the 9-P(38) and 10-R(38) CO₂ laser Lines. Line assignments are proposed and new FIR laser lines are reported.     

Assignments of optically pumped CD3OH laser lines

Six FIR laser lines from CD₃OH pumped by the 10R(36) and the 10R(18) CO₂ laser lines are assigned to specific rotational energy levels in the excited C–0 stretch state. It is found that their upper laser levels are shifted by a Fermi resonance between the C–0 stretch vibration and the third and forth harmonics of the torsional mode. The Fermi resonance shifts are +0.332 cm^–1 and +2.251 cm^–1 for the upper laser levels pumped by the 10R(36) and the 10R(18) CO₂ laser lines, respectively. Calculated frequencies of the pump and the laser transitions agree with those of the pump CO₂ laser lines and the observed FIR laser lines within estimated accuracy.     

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     

Electric field effects on an optically-pumped HCOOH FIR laser and Zeeman laser theory

Electric field effects have been investigated on the output power of six far-infrared (FIR) laser lines from H¹²COOH optically-pumped by a CO₂ laser with its polarization arranged perpendicular to the Stark field. Optoacoustic signals observed on the pump lines were hardly affected by the applied electric field up to 0.6 kV/cm. By neglecting the electric field effects on the pump transitions, Zeeman laser theory has been applied to the FIR laser transitions. Numerical calculation predicts the observed FIR output power as a function of electric field. Experessions for oscillation frequency and intensity in homogeneous limit are given, which may be applicable to any FIR Stark laser so far as the pump transition is free from electric field effects.     

13CD3OH and12CD3OH optically pumped by a13CO2 laser: Observations and assignments of FIR laser lines

In this work we report the first observation of FIR laser lines from¹³CD₃OH pumped by the¹³CO₂ isotope laser. Using the same pump we have also found 3 new lines from¹²CD₃OH. Tentative assignments for the absorption and emission transitions of the observed lines are also proposed.Work supported by FAPESP. CNPq, FAEP/UNICAMP-Brasil and NSF-USA     

Collisional transfer of rotational energy in the 2B1 electronic state of nitrogen dioxide

Collisional satellite lines have been observed in fluorescence from nitrogen dioxide excited by the 4545-Å line of the argon laser. The 13_0,13 level of the (0, 8, 0) vibrational state is populated by the laser and undergoes collisionally induced transitions to the 11_0,11, 15_0,15, and 17_0,17 states. These collisionally populated states are identified by their fluorescence to the well-studied (0, 0, 0) and (0, 1, 0) levels of the ground electronic state. These satellite lines are also observed in fluorescence to the (0, 2, 0) and (0, 3, 0) vibrational levels of the ground electronic state. The wavenumbers of those lines, together with those from unrelaxed fluorescence and previously published microwave transitions, allow vibrational and rotational constants for the higher vibrational states to be determined more accurately than was previously possible. Several much weaker forbidden transitions have also been observed, including ΔK_a = 0 through ?6 transitions in the (0, 8, 0)-(0, 0, 1) band.     

Infrared laser induced fluorescence as a spectroscopic probe: Applications to CO2

Use of the infrared laser induced fluorescence technique as a spectroscopic probe is discussed with applications to CO₂. It is shown how the shape of the fluorescence signal can be used to easily distinguish between fundamental and hot band transitions. Fluorescence and absorption experiments have also been performed with ¹³C enriched CO₂ and result in probable assignments of CO₂ transitions for a number of HBr laser lines which are absorbed by CO₂.     

Far-Infrared Laser Assignments for Methylamine

Reported far-infrared laser lines for five different transition systems of CH₃NH₂ optically pumped by a CO₂ laser have been identified spectroscopically through a high-resolution Fourier transform infrared study of the C-N stretching band together with CO₂-laser/microwave-sideband broad-scan and Lamb-dip measurements. From the infrared analysis plus previous far-infrared (FIR) results for the ground vibrational state, quantum numbers have been assigned for seven methylamine FIR laser transitions and their C-N stretching pump absorptions coincident with the CO₂ laser lines. The assignments are confirmed through the use of closed frequency combination loops that also provide improved FIR laser frequencies to spectroscopic accuracy.     

Observation and assignment of submillimetre laser lines from CH3OH pumped by isotopic CO2 lasers

New laser lines have been generated using methanol when isotopically labelled CO₂ is used in the pump laser. 19 lines have been found when¹³C¹⁶O₂ is used and 29 when¹²C¹⁸O₂ is used. The wavelengths of the emission lines have been measured with a relative accuracy of 5×10^–3 using the submillimetre resonator as a scanning Fabry-Perot interferometer, and the polarizations of the lines have also been measured. Some of the laser lines have been assigned to pure rotational transitions in the excited state associated with the CO stretching mode, other lines are believed to originate from pumping in combination bands.     

New far infrared laser lines from 13CH2F2 and frequency measurements

We report new FIR laser lines from ¹³CH₂F₂ molecules optically pumped by a waveguide CO₂ laser. The increased tunability (300 MHz) with respect to a conventional CO₂ laser allows the pumping of ¹³CH₂F₂ vibrational transitions of large offset. 34 new laser lines have been discovered, ranging from 113.1 m to 491.4 m in wavelength, thus increasing the number of known FIR laser lines from this important molecule to 99. For all the new lines and many (36) of those known previously, precise offset measurements through the transferred Lamb-dip technique were performed. The frequency of six new laser lines was also directly measured by heterodyne detection with known laser lines.