New FIR laser lines from hydrazine and assignments

Our new waveguide pulsed CO₂ laser, with peak powers above 1 kW, has allowed us to observe 24 new far-infrared laser lines emitted by hydrazine. Each of them is characterized in wavelength, relative polarization, intensity, optimum operating pressure and pump offset from the center of the exciting CO₂ line. These new laser emissions either form pairs sharing the same pump line, or complete such pairs with lines known from the literature. In the latter case, we have measured the relative polarization and offset of the partner lines whenever they were not reported in the literature. The availability of laser systems with two emission lines orthogonally polarized and sharing the same upper level is expected to facilitate the assignment work. We present complete assignments for four FIR laser emissions, and we propose J and K values for 12 further laser systems. PACS 42.55.Lt; 42.62.Fi     

Confirmation of far infrared laser assignments from CH3-deformation and CH3-rocking states of optically pumped methanol

High-resolution Fourier transform spectroscopy has been applied to confirm previously proposed assignments for nine far infrared (FIR) laser lines from the CH₃-deformation state of CH₃OH and one line from the CH₃-rocking state. Accurate frequencies are deduced for the observed and other predicted FIR laser transitions. FIR torsional branch frequencies in the ground state which were used in the confirmation are presented. Comments are also made on the OH-bending mode of CH₃OH.     

Applications of high resolution spectroscopy to the identification of far-infrared laser emission from optically pumped13CH3OH

High-resolution infrared (IR) and far infrared (FIR) Fourier transform absorption spectra have been employed to investigate assignments of FIR laser lines reported from optically-pumped¹³CH₃OH. The spectroscopic measurements are used in conjunction with the reported IR pump and FIR laser frequencies to form closed combination loops for several systems, serving to confirm the assignments and in some cases to improve the accuracy of the FIR laser frequencies. Frequency predictions from combination differences are also presented for a number of potential new FIR laser lines.     

Laser-induced fluorescence spectrum of argon matrix-isolated dichlorocarbene

Dichlorocarbene has been prepared for spectral investigation by the matrix reaction of alkali metal atoms with carbon tetrachloride at high dilution in argon followed by condensation onto a copper wedge held at 15 K. When these samples were irradiated with laser lines of wavelengths between 5682 and 4545 Å, an intense red emission system peaking around 7000 Å was observed. The spectrum of this emission revealed at least five progressions in the ground state bending and stretching fundamentals. A revised value of the ground state bending mode for CCl₂ was obtained from higher-resolution spectra using more diluted samples and various laser exciting frequencies. Carbon-13 enriched samples confirm the assignments of the bands to progressions in the ground state bending and symmetric stretching modes of CCl₂.     

Assignments of optically pumped CH3OD laser lines

Fifteen laser lines from CH₃OD pumped by a CO₂ laser are assigned to specific rotational energy transitions. These assignments have been obtained from the approximation that, except for one constant, the molecular constants in the excited CO stretching state are same as those in the ground state.     

New CH2F2 FIR laser lines pumped by a tunable WG CO2 laser

8 new large offset FIR laser lines of CH₂F₂ have been discovered by pumping with a high tunability waveguide CW CO₂ laser. Optoacoustic measurements of CH₂F₂ have also been performed and the pump offsets of the new and of previously known lines have been measured and checked. Some assignments are proposed and a few assignments found in literature are checked     

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.     

Infrared-microwave double resonance as an aid in assignment of optically pumped submillimetre laser lines: CH2CF2, CH2F2, and CH3OH

Infrared-microwave double resonance has been used to confirm recent assignments of optically pumped submillimeter wave laser lines in CH₂CF₂ and CH₃OH, as well as a tentative assignment of a line in CF₂H₂. Intracavity double resonance signals have also been obtained in CF₂CH₂ using a circular copper waveguide laser.     

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.     

Pulsed optically pumped far infrared laser and maser action in OCS

Twenty new optically pumped far-infrared laser transitions have been observed in OCS, including four “maser” transitions of 3.6–8.2 mm wavelength. The operating conditions and assignments of these lines are reported. Rabi splitting of the FIR gain profile caused by the high intensity of the CO₂ TEA laser pump is found to be very important for some lines.     

Resonance series of Br2 in the vacuum ultraviolet

A high-resolution resonance fluorescence spectrum of bromine excited by an electrical discharge in the region 1500–2100 Å was photographed on a 10.7-m concave grating vacuum spectrograph. Twelve resonance doublet series excited by four bromine atomic resonance lines were identified and analyzed. All doublet series have the ground state of ^79,81Br₂ as the lower electronic state. The vibrational numbers of these doublets corresponding to this state vary from 0 to 76. Rotational constants are obtained by least-squares fitting of the doublet separations, and the vibrational constants by least-squares analysis of vibrational term values. Probable assignments for the upper electronic state(s) of the transitions involved were suggested.     

Acoustooptic extension of the frequency tunability of CW CO2 lasers: New FIR lasers emissions from CH3OH and13CH3OH

We have increased the frequency tunability of our CW waveguide CO₂ lasers by means of an acoustooptic amplitude modulator, operating at the fixed frequency of 90 MHz. The up-shifted, or down-shifted, laser optical sideband can be generated independently by adjusting the orientation of the modulator. The efficiency is larger than 50%. The frequency tunability of the CO₂ laser around each laser line is thus increased by 180 MHz. To demonstrate the possibilities of this method, a source composed of the above modulator and of a CW, 300 MHz tunable waveguide CO₂ laser has been used for the search of new large offset FIR laser lines from optically pumped CH₃OH and¹³CH₃OH molecules. As a result 15 and 10 new large offset laser lines were discovered respectively. New assignments of some laser lines are also proposed. We have also measured the Stark effect, the offset, and the polarization of other already known lines. In particular a Stark effect frequency tuning of about 1 GHz is demonstrated for a laser line at 208.399 m.     

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.     

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 far-infrared emissions and frequency measurements in hydrazine

By means of a new CO₂ laser we performed a new investigation of the far-infrared laser emission spectrum of hydrazine excited by the 10P(32) and 10R(8) CO₂ laser lines. We found seven new lines and measured the frequency of four of them; moreover we measured the frequencies of two more lines previously reported in the literature with only wavelength measurements. The frequencies of the far-infrared laser emissions have been measured by means of a frequency-synthesis chain based on new InP Schottky diodes. The detected signal was beat-note generated in a Schottky diode between the far-infrared radiation, the harmonics of a 72 GHz frequency reference and a rf signal. We also characterized all of the observed lines by their polarization relative to the pumping CO₂ laser, the optimum pressure and the offset relative to the CO₂ center frequency. PACS 42.55.Lt; 42.62.Fi     

Measurements and assignments of new large offset CD3OH FIR laser lines

By using an acoustooptic modulator we extend the 300 MHz tunability of a waveguide CO₂ laser to 480 MHz. The CD₃OH was optically pumped by the 10R(32), 10R(34), and 10R(36) CO₂ laser lines, and 17 new FIR laser lines were discovered. The Stark effect on previously known FIR laser lines was investigated, and some tentative FIR laser lines assignments are suggested.     

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

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.     

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.     

Fourier Transform Infrared spectrum of the OCD bending mode in methanol-D1

The infrared (IR) spectra corresponding to OCD bending vibration of asymmetrically deuterated methanol species CH₂DOH have been recorded with a Fourier Transform Spectrometer. The spectrum shows a typical structure of a parallel a-type band. This is expected because the bending vibration mainly executed parallel to the symmetry axis The Q-branch lines are grouped closely around 896 cm⁻¹ and the P- and R-Branches show complex structure. Nonetheless it was possible to assign a-type P- and R-branch lines up to K value of 8 and J value up to about 20 in most cases. The Q-branch lines for higher K values can be followed to about J = 15, the presence of which confirmed the assignments. The observations suggest that in the OCD bend some energy levels are highly interacted by highly excited torsional state from the ground torsional state. A full catalogue is presented along with the effective molecular parameters. An intensity anomaly was also observed in the transitions. So far it has been possible to assign only transitions between e₀ ← e₀ states. Plausible explanations of intensity anomaly are presented. Lastly, a number of optically pumped far infrared (FIR) laser lines have been assigned either to exact or tentative quantum states. These assignments should prove valuable for production of new FIR laser lines.     

Reanalysis of the C1Πu state of Na2 based on ultraviolet argon ion laser fluorescence

Six uv lines of an argon ion laser (CR-18 UV) are used to excite the C¹Π_u state of the Na₂ molecule. There are nine fluorescence series observed, two of which are excited from a fairly high vibrational level (v″ ≥ 11) in the ground state. A careful study of the intensities of these transitions reveals that the previous vibrational assignments of the energy levels in the C¹Π_u state are incorrect (too high by 2). A new analysis for this state was carried out and resulting molecular parameters are presented.