The rotational spectrum of the NH+ radical in its X 2Pi and a 4Sigma- states.

Transitions between the spin-rotational levels of the (14)NH(+) radical in the v = 0 levels of its X (2)Pi and a (4)Sigma(-) states have been studied by the technique of laser magnetic resonance at far-infrared wavelengths. The data have been combined with a previous zero-field measurement of the J = 1 1/2 - 1/2 transition frequencies at 1.01 THz to determine a much improved set of molecular parameters for NH(+) in the X (2)Pi state; the major parameters for the a (4)Sigma(-) state have also been determined.

Tunable far-infrared spectroscopy extended to 9.1THz.

We synthesized tunable far-infrared radiation at frequencies higher than 9 THz (300 cm (-1)) by mixing CO(2) laser, (15)NH(3) laser, and microwave radiation in a W-Co metal-insulator-metal diode. We used this farinfrared radiation to accurately measure torsion-rotation transitions of CH(3)OH in the 8-9-THz region. We also measured the frequency of the aP(7, 3) (15)NH(3) laser transition.

The rotational and fine-structure spectrum of FeH, studied by far-infrared laser magnetic resonance.

Transitions between the spin-rotational levels of the FeH radical in the upsilon=0 level of the X (4)Delta ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. Both pure rotational and fine-structure transitions have been observed; lambda-type doubling is resolved on all the observed transitions. The energy levels of FeH are strongly affected by the breakdown of the Born-Oppenheimer approximation and cannot be modeled accurately by an effective Hamiltonian.

Far-Infrared Laser Magnetic Resonance Spectroscopic Study of the nu(2) Bending Fundamental of the CCN Radical in Its &Xtilde;(2)Pi(r) State.

Bending vibration-rotation transitions between the (010) µ(2)Sigma(-) and (000) (2)Pi(r) vibronic states of the CCN radical in its ground electronic state have been observed using far-infrared laser magnetic resonance (FIR LMR) spectroscopy. Thirteen FIR laser lines were used to record 769 resonances. The LMR data, combined with previous data, were used to determine vibrational, Renner-Teller, fine-structure, rotational, hyperfine, and molecular g-factor parameters using a least-squares fitting routine.

Rotational Spectrum of the AsH(2) Radical in Its Ground State, Studied by Far-Infrared Laser Magnetic Resonance.

The rotational spectrum of AsH(2) in its ground &Xtilde;(2)B(1) electronic state has been recorded using a far-infrared laser magnetic resonance spectrometer. The AsH(2) radical was produced inside the spectrometer cavity by the reaction of arsine (AsH(3)) with fluorine atoms. Hyperfine splittings from both (75)As and (1)H nuclei were observed, and analysis of the spectra has yielded accurate values for rotational, hyperfine, and Zeeman parameters.

Far-Infrared Rotational and Fine-Structure Transition Frequencies and Molecular Constants of 14NO and 15NO in the X2Pi (v = 0) State.

We have made highly accurate measurements of the absorption spectrum of the 14NO and 15NO isotopomers of nitric oxide in the far-infrared. Pure rotational transitions up to J" = 3712 within the 2Pi1/2 and 2Pi3/2 spin components and several 2Pi3/2 <-- 2Pi1/2 fine-structure transitions were recorded within the ground vibrational state. A least-squares fit to these data combined with some lambda-doubling and rotational transitions measured by previous workers has resulted in accurate values for the rotational, fine, and hyperfine parameters of these two isotopomers.

Optically Pumped FIR Laser Lines from CH3OH: New Laser Lines, Frequency Measurements, and Assignments.

We report the identification and characterization of eight new FIR laser lines from methanol (CH3OH) in the range 48.4 to 453.7 µm pumped by sequence and hot bands of a cw CO2 laser.

Frequencies of Optically Pumped Sub-Doppler Far-Infrared Laser Lines of Methanol.

Sub-Doppler signals from the gain curves of four lines of a transversely pumped far-infrared methanol laser were used to stabilize the frequencies of the laser. The frequencies of four of the strongest FIR laser lines (70, 119, 123, and 570 µm) were measured. Lasers locked to these lines have a frequency reproducibility of a few parts in 10(8) and an uncertainty of less than 30 kHz.

Sub-Doppler Frequency Measurements of 15NH3 Laser Transitions.

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C-13 Methanol Far-Infrared Laser: Newly Discovered Lines, Predictions, and Assignments.

We report 25 new laser lines from 13CH3OH methanol when pumped by a cw CO2 laser. The majority of the lines are pumped by the 10R (regular) and 10SR (sequence) bands of the CO2 laser. Two are pumped by the 9HP(20) hot-band CO2 line.

Far-Infrared Rotational Spectra of ZnH and ZnD in the X2Sigma+ (v = 0) State.

Several rotational transitions of zinc hydride and deuteride within the v = 0 level of the X2Sigma+ state have been measured in both electron spin components over the ranges N" = 2 to 10 for ZnH and N" = 9 to 21 for ZnD. A least-squares fit to these data in combination with low-N microwave data measured by other workers has resulted in improved values of the rotational, fine, and hyperfine structure constants. The values of the proton hyperfine constants are discussed in the context of a molecular orbital analysis of zinc hydride.

Extension of tunable far-infrared spectroscopy to 7.9THz.

We generated tunable far-infrared radiation by mixing CO(2) -laser,(15)NH(3) -laser, and microwave radiations in a W-Co metal-insulator-metal diode. We used this far-infrared radiation to measure accurately the torsion-rotation transitions of CH(3)OH in the 6-8-THz region.

Sequential optical pumping of a far-infrared ammonia laser.

We present a novel technique for resonantly pumping a continuous-wave far-infrared NH(3) laser with a linetunable mid-infrared NH(3) laser that is optically pumped by a CO(2) laser. In this two-step process we first convert 10-microm CO(2) laser photons into 11-13-microm NH(3) laser photons, which are then converted into 60-400-microm photons in a far-infrared NH(3) laser. Continuous-wave laser action on 10 far-infrared lines of (15)NH(3), including four new ones, has been obtained with a single CO(2) laser pump line.

Far-infrared continuous-wave laser emission from H2O and from NH(3) optically pumped by a CO laser.

We report what we believe is the first observation of continuous-wave far-infrared laser emission from water vapor and from ammonia optically pumped by a CO laser.

Short-wavelength far-infrared laser cavity yielding new lines in methanol.

We report 16 new laser lines generated in a short-wavelength far-infrared Fabry-Perot laser cavity. The CO(2) pump laser is coupled into the far-infrared laser outside the far-infrared laser mode, and the cavity uses a 45 degrees adjustable output coupling mirror; this combination results in a low-loss Fabry-Perot cavity for wavelengths below 150 microm. The new lines are of medium and strong intensity and have wavelengths in the region 26.

Sub-Doppler tunable far-infrared spectroscopy.

The first experimental observations to our knowledge of sub-Doppler linewidths in a cell made using tunable far-infrared radiation are reported. A double-resonance scheme has been used, combining CO(2)-laser infrared radiation with tunable far-infrared radiation to observe a sub-Doppler line shape in an excited vibrational state of CH(3)OH.

Pressure effects on the frequency of continuous-wave optically pumped far-infrared lasers.

The frequency of the 170.6-microm cw CH(3)OH optically pumped laser emission has been remeasured at different pressures without observing the pressure shift observed by Lawandy and Koepf [Opt. Lett.

Direct frequency measurement of the I(2)-stabilized He-Ne 473-THz (633-nm) laser.

The absolute frequency of the 473-THz He-Ne laser (633 nm), stabilized on the g or i hyperfine component of the (127)I(2) 11-5 R(127) transition, was measured by comparing its frequency with a known frequency synthesized by summing the radiation from three lasers in a He-Ne plasma. The three lasers were (1) the 88-THz CH(4)-stabilized He-Ne laser (3.39 microm), (2) a 125-THz color-center laser (2.

Direct frequency measurements of transitions at 520 THz (576 nm) in iodine and 260 THz (1.15 microm) in neon.

The o hyperfine component of the (127)I(2) 17-1 P(62) transition at 520 THz (576 nm) in iodine was measured with respect to the CH(4)-stabilized 88-THz He-Ne laser. A 26-THz CO(2) laser, a color-center laser at 130 THz, and a He-Ne laser at 260 THz were used as transfer oscillators. The measured I(2) frequency was 520 206 808.

Additional cw FIR laser lines from optically pumped CH(2)F(2).

Twenty-five new, cw, FIR lines from CH(2)F(2), optically pumped by a CO(2) laser, have been found, using a variablecoupling, open-structure resonator. Accurate wavelength measurements have been made on the 47 known CH(2)F(2) lines. The new lines are fairly uniformly distributed over a wide range, from 105 to 1448 microm.