Ν3 Fundamental Band Research Articles

Laser action at 12.812 μm in optically pumped NH3

Optical pumping of the aR (6,0) line of the ν2 fundamental vibrational band of NH3 has led to laser action on the aP (8,0) line at 12.812 μm of the same vibrational band. A 5-kW pulsed output has been obtained by using 1.5 MW of pump power at 9.294 μm from a CO2 laser.

Analysis of tunable diode laser spectra of the ν4 band of 12C316O2

Current-tunable thin-film PbTe diode lasers have been used to obtain Doppler-limited resolution of the ν4 asymmetric stretch band of C3O2 in the region 1565–1600 cm−1. Roughly 70% of the interval was covered using different modes of three lasers, each mode giving a tuning range of 1–3 cm−1. Absolute spectral calibration was obtained from NH3 and H2O, together with the channel spectrum of a 4-cm Ge etalon recorded simultaneously using a double beam technique. Rotational constants were determined for the ν4 fundamental band and five different hot bands associated with the thermally excited low frequency bending mode ν7. The band origin for the ground state transition is 1587.390±0.002 cm−1 and the ν7 hot bands are shifted progressively to lower frequency. The systematic shift of the hot bands was verified independently with temperature difference spectra from a Fourier transform spectrometer.

High-resolution infrared spectrum of CH 2D 2: The ν3 fundamental band at 7 μm

The infrared spectrum of CH 2D 2 has been recorded in the region of 1345 to 1561 cm −1 with a resolution of 0.030 to 0.026 cm −1. Most of the observed lines have been assigned to transitions of the ν 3 band of CH 2D 2. However, 114 lines have been identified as transitions of the ν 2 band of H 2 16O whose band origin has been directly determined to be 1594.7472 ± 0.0030 cm −1. A few weak lines, probably belonging to the ν 5 fundamental of CH 2D 2, remain unassigned. The band center ν = 1435.1326 ± 0.0030 cm −1 and a set of upper state constants were obtained for the ν 3 band of CH 2D 2. Although a slight perturbation was noticed in the ν 3 band, all wavenumbers have been fitted with a standard deviation of 3.8 × 10 −3 cm −1.

High resolution infrared spectrum of CH 2D 2: The ν1 and ν6 fundamental bands near 3000 cm −1

The spectrum of CH 2D 2 between 2865 and 3165 cm −1 has been investigated under high resolution with a Fourier-transform interferometer. Two fundamental bands have been analyzed, the B-type band ν 1 and the C-type one ν 6. These two bands are more or less perturbed. It was possible to compute more than 1100 ground-state combination differences. These 1100 data allowed the determination of ground-state constants: A o = 4.3027777(38), B O = 3.5058838(35), C O = 3.0500599(37), Δ J = (0.46419 ± 17)10 −4, Δ JK = (−0.15781 ± 58)10 −4, Δ K = (0.72997 ± 60)10 −4, δ J = (0.088372 ± 90)10 −4, δ K = (−0.14948 ± 64)10 −4 (all in cm −1). We obtained a standard deviation of 0.0008 cm −1.

The ν2 band of CHD3: Ground-state parameters for CHD3 from combination differences

The ν2 fundamental band of CHD3, centered near 2143 cm−1, has been recorded at a resolution of 0.015–0.025 cm−1. Analysis of ground-state combination differences has yielded well-determined values for the ground-state molecular parameters B0, D0J, D0JK, H0J, H0JK, and H0KJ for CHD3. These parameters have been used in the determination of the molecular parameters α2B, (α2A - α2B), β2K, β2JK and β2J for ν2.

The ν2 fundamental vibration-rotation band of T2O

The ν2 fundamental vibration-rotation band of T2O vapor has been measured at grating resolution, and the rotational structure has been analyzed. The band center and the values of the rotational constants A, B, and C for the ground state and excited state have been determined. These values are consistent with the data for J through 6, and with extrapolation from H2O and D2O.

The development and evaluation of a cryosorption pump capable of pumping all gases including helium: Ronald Dawbarn and J D Haygood, ARO, Inc, Aerospace Environmental Facility, Arnold Engineering Development Centre, Arnold Air Force Station, Tennessee, USA

New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of ±0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200–1800 cm−1 spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the ν4 fundamental band of 13CH4 indicated that an empirical power law used for the temperature dependence of the N2-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17], [18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.

Integrated Intensity of 33-μ Band of Methane*

The ν3 fundamental band of CH4 was studied by application of the Goody statistical band model to small frequency intervals within the band. The band parameters were established from low-resolution measurements, and the spectral absorption coefficient was derived for 42 frequencies in the band. The integrated band intensity was found to be 290±15 cm−2 atm−1 at 273°K.

Infrared chemiluminescence and vibraluminescence in the NO — O — NO2 reaction system

Infrared emission from the low-pressure gas-phase NO — О reaction system has been studied from 1 to 7,0 microns. An infrared integrating sphere has been used for the reaction cell to provide increased lightgathering efficiency, and because of the relatively weak source, the emission spectra were obtained with an interferometer spectrometer. The « continuum « associated with the NO + O recombination decreases monotonically and extends to at least 3,7 microns. Vibrational-rotational spectra from NO and NO2 have been observed and their relative intensities studied versus concentrations of the reactants. An unidentified band is observed at 3,7 microns whose intensity varies directly with the intensity of both the continuum and the NO2 ν3 fundamental at 6,3 microns. The intensity of the vibrational-rotational emission relative to the continuum radiation has been found to be pressure-dependent due to the considerably different radiative lifetimes and collisional deactivation processes involved. The ν3 fundamental band of NO2 at 6,3 microns excited by chemiluminescence in the NO + О → NO2 * reaction is broader and, therefore, excited to higher vibrational levels than it is when excited by vibrational exchange with O2 [math] (vibraluminescence). The vibrational excitation of O2 occurs in the fast reaction NO2 + О → NO[math] + O2 [math]. Chemiluminescence from NO[math] is also observed in this reaction which demonstrates excitation of both the newly formed bound and the unbroken bond simultaneously.

High-Temperature Spectral Emissivities and Total Intensities of the 15-μ Band System of CO_2*

Spectral-emissivity measurements of the 15-μ band of CO2 were made in the temperature range from 1000° to 2300°K. The hot gas was produced in a supersonic burner, which used gaseous carbon monoxide and oxygen as propellants. Many “hot” transitions were observed which were identified through their Q-branches even when the spectral resolution of the spectrometer was not very high. The total intensity of the ν2-fundamental band system was determined at the highest temperatures and a value of 240 ± 15% cm−1/cm at STP was obtained in the present experiment which is in agreement with other measurements at room temperature. The maximum error resulting from the presence of the strong central Q-branch (at 670 cm−1) at a temperature of 2300°K was estimated, utilizing detailed line calculations for the fundamental transition and band-model calculations for the higher-order transitions.