Self-broadened widths and absolute strengths of 12CH4 lines in the 1310–1370 cm-1 region

Self-broadened widths and absolute strengths of ¹²CH₄ lines in the 1310–1370 cm^-1 spectral region have been measured at room temperature (296 K) using Fourier transform absorption spectroscopy with a 0.003 cm^-1 resolution (FWHM unapodized). The line widths, which are the most comprehensive set of measurements on self-broadened lines in the ν₄ R-branch yet reported, show a tetrahedral-symmetry dependence, which is consistent with recently reported observations. Generally, the line strengths are approximately 5% higher than those tabulated on the AFGL line-parameter compilation.     

Laser Lines and Frequency Measurements of Fully Deuterated Isotopomers of Methanol

Fully deuterated isotopomers of methanol (¹²CD₃OD and ¹³CD₃OD) were optically pumped with a CO₂ laser. Five new far-infrared laser lines were discovered in ¹²CD₃OD and 25 in ¹³CD₃OD in the range 43.697 to 719.426 m. The frequencies of these new and some previously reported laser lines, the pump offset, the relative polarization, the relative intensity, and the optimum pressure of operation were measured.     

Line-shape parameters of the Raman lines of chloro-, bromo-, and iodobenzene

High-resolution Raman spectra have been measured of chloro-, bromo-, and iodobenzene for line shifts up to 1600 cm⁻¹ and several new lines were resolved. The line-shape parameters and depolarization ratios of most of these lines are reported here for the first time. The 1595 cm⁻¹ benzene E_2g doublet was resolved into the A₁ and B₁ monohalogen substituted lines. In going from bromoto iodobenzene a reversal in the A₁-B₁ line intensities was observed.     

The rotationally-resolved absorption spectrum of formaldehyde from 6547 to 6804 cm

The room temperature absorption spectrum of formaldehyde, H₂CO, from 6547 to 6804 cm⁻¹ (1527-1470 nm) is reported with a spectral resolution of 0.001 cm⁻¹. The spectrum was measured using cavity-enhanced absorption spectroscopy (CEAS) and absorption cross-sections were calculated after calibrating the system using known absorption lines of H₂O and CO₂. Several vibrational combination bands occur in this region and give rise to a congested spectrum with over 8000 lines observed. Pressure broadening coefficients in N₂, O₂, and H₂CO are reported for an absorption line at 6780.871 cm⁻¹, and in N₂ for an absorption line at 6684.053 cm⁻¹.     

Diode laser spectra of the ν2 band of H212CO and H213CO

The Q-branches of the ν₂ (CO stretch) band of H₂¹²CO and H₂¹³CO have been studied in high resolution using an infrared diode laser. Accurate upper state constants, including A, B, C, Δ_J, Δ_JK, Δ_K, and H_K, were determined from an analysis of the data for 97 lines of H₂¹²CO and 79 lines and H₂¹³CO and compared with previous reported values. Band centers were also determined and reported as 1746.009 ± 0.002 cm^?1 for H₂¹²CO and 1707.981 ± 0.002 cm^?1 for H₂¹³CO.     

New FIR laser lines and frequency measurements for optically pumped CD3OH

Twenty new cw FIR laser lines in CD₃OH, optically pumped by a CO₂ laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO₂ lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 10⁷.Contribution of the U.S. Government, not subject to copyright.     

Heterodyne frequency measurements of COF2, CD3F,13CD3F, and C2H5I lasers

Heterodyne frequency measurements are reported for twenty optically pumped laser lines from various molecules including COF₂, CD₃F,¹³CD₃F, and C₂H₅I.     

Methanol laser lines from torsionally excited co stretch states, and from OH-bend, CH3-rock, and CH3-deformation states

Using a quasi-CW CO₂ oscillator-amplifier combination with peak power 300 Watt, we have generated FIR laser emission in weak absorption bands of CH₃OH. 40 new lines are reported, and their wavelengths are measured with a relative accuracy of 5×10^–5. A total of 72 lines are assigned. 34 of these involve torsional n=1, 2, and 3 states of the CO stretch and the vibrational ground state. The remaining lines are associated with the CH₃-rock, OH-bend, and CH₃-deformation modes. The latter are located 1460 cm^–1 above the ground state, and are pumped by simultaneous vibrational excitation and torsional deexcitation.     

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.     

Shifts of X-ray characteristic L lines of free atoms of rare-earth metals

Results of the study of X-ray characteristic spectra of free atoms of a number of rare-earth metals from Ce to Ho are reported. L _α1 and L _β1 lines were studied, and the shifts of the peaks of emission lines of free atoms relative to their positions in the case of emission by the solid aggregate state were measured. The data obtained enable one to use the corresponding X-ray characteristic lines as references with the accuracy Δλ/λ≈10^?5. The Z-dependences of shifts are plotted.     

Tunable diode laser measurements of absolute linestrengths in the HNO3 ν2 band near 5.8 μm

Absolute linestrengths of selected lines in the υ₂ band of HNO₃ have been measured using a tunable diode laser spectrometer operating in a sweep integration mode. The direct measurement technique has been employed to obtain line intensities at 296 K for 22 isolated lines in the 1720–1725 cm^-1 region. The reported linestrengths have estimated uncertainties of 4%, a significant portion of this uncertainty arising from spectral interference from hot band transitions. From these linestrength measurements, an integrated band intensity of 1375 cm^-2-atm^-1 at 296 K is inferred.     

EPR of the ferroelectric phase transition in Li2Ge7O15:Cr3+ crystals

A Cr³⁺ EPR study of lithium heptagermanate crystals, Li₂Ge₇O₁₅ (LHG), close to the phase transition is reported. Orientation dependences of the spectra in the paraelectric phase of LHG have been measured. An anomalous broadening of the resonant lines accompanied by a crossover in their shape was found in the vicinity of the transition point. Doublet splitting of the EPR lines was observed to occur below T _C as a result of emergence of two structurally nonequivalent positions for Cr³⁺ ions. Fiz. Tverd. Tela (St. Petersburg) 40, 1102–1105 (June 1998)     

Anisotropy of hyperfine field in diamagnetically substituted YIG

The results of the nuclear magnetic resonance of ⁵⁷Fe in Al-, Ga- and In-substituted Y₃Fe₅O₁₂ garnets are reported. When diamagnetic Ga³⁺ or Al³⁺ ions are substituted for tetrahedral Fe³⁺ ions, four satellite lines in the NMR spectrum of octahedral Fe³⁺ ions appear. The substitution of In³⁺ ions for octahedral Fe³⁺ ions leads to three satellite lines in the spectrum of tetrahedral Fe³⁺ ions. The hyperfine fields of these satellites are explained using the independent bond model for the hyperfine interaction. Suprisingly large change of the anisotropic part of the hyperfine field relative to the isotropic one was found.     

Effective oscillation of a cw CO2 laser in the range of 11μm (011 1–111 0 band)

Results are reported of the optimization of a cw CO₂ laser emitting at lines of the hot 01¹1–11¹0 band. The achieved output power of 6 W amounts to 40% of the power obtained on the regular 00¹1–10¹0 band in the given system under the optimal conditions.     

Shift measurements of Hα and Hβ lines in arc plasmas

Red shifts are reported for the H_α and H_β lines at electron densities of 10¹⁶–10¹⁷ cm^-3. The peak shift of the H_α line agrees with the ELC shift. For the H_β line, the dip shift exceeds the ELC shift systematically. The H_β dip shift is proportional to N_e/T.     

Fast excited-state relaxation of Eu-Eu pairs in commercial Y2O3: Eu3+ phosphors

Low-temperature, dye-laser excitation spectroscopy of commercial Y₂O₃:Eu³⁺ phosphors reveals the presence of complex structure in the excitation lines of the ⁵D₀ and ⁵D₁ manifolds. The structure is associated with the presence of Eu³⁺ ion pairs. The kinetics of the emission decay are observed to be drastically different when excitation occurs either at the center or on the wings of the excitation lines, suggesting faster inter-level and/or inter-site energy transfer on exciting into the line wings. Low-temperature vibronic spectra are reported for the ⁷F₀→⁵D₀ transitions for both C₂ and C_3i sites. Evidence is presented for the detection of the highly forbidden ⁷F₀→⁵D₀ transition for the C_3i site.     

Laser induced emission spectra of Pr3+ in CaF2 at low temperatures

The luminescence spectra of Pr³⁺ in CaF₂, excited with the 4765.05 Å line of the argon ion laser at low temperatures, consist of many more emission lines than the maximum allowed via the ³P₀→³H_4,5,6; ³F_2,3,4 transitions of a single Pr³⁺-site. Based upon their intensity, appropriate splittings and concentration dependence, these emission lines are divided into three groups, attributed to different sites of Pr³⁺ in CaF₂. The existence of Pr³⁺ ions in defect sites of different symmetries is supported by theoretical calculations. The laser emission spectra of Pr³⁺ at low temperatures are compared with room temperature emission spectra obtained with excitation of the ³P₀ state alone, and with low temperature spectra of Pr³⁺ in different hosts, reported in the literature.     

Far-infrared photoconductivity spectra of quenched-in acceptors in Germanium: absorption and photo-thermal ionization lines of two new shallow acceptors

The far-infrared photoconductivity spectra of germanium crystals quenched from T>800C show three new sets of hydrogenic acceptor excitation lines, in addition to the 8.69 meV (SA^'₁) and 9.48 meV (SA^“₁) acceptor series reported earlier. The corresponding ground state binding energies are 13.89 meV (SA^'₂), 14.42 meV (SA^“₂), and 17.89 meV (SA₃). We tentatively attribute both the SA^'₂ and the SA^“₂ line series to one acceptor complex with a multiple ground state. At high acceptor concentrations the excitation lines are seen as sharp minima superimposed on a continuous photoconductivity background. With decreasing acceptor concentration, or increasing temperature, they gradually evolve into the familiar positive-going photo-thermal ionization peaks. This is explained by the different concentration and temperature dependence of the cross-sections for the absorption and photo-thermal ionization mechanisms.     

Line assignments and intensities for the ν3 + ν4 − ν4 band of 12CH4

Assignments and Intensities are reported for 886 lines arising from the “hot-band” ν₃ + ν₄ ? ν₄ of ¹²CH₄ at 3.3 μm. These are determined from spectra at 0.01–0.02 cm^?1 resolution that include intensity measurements at reduced temperatures. Energy levels for the v₄ = 1 state through J = 12 are also given based on the ν₃ + ν₄ band assignments of Hunt et al., and the wavenumbers of the hot-band lines.