Broadening, shifting, and line mixing in the 030 ← 010 parallel Q branch of N2O

The 03¹0 ← 01¹0 parallel Q branch of N₂O has been studied at 297 K and over the pressure range 1-130 torr. Absorption spectra were recorded using a high resolution (1.5 MHz or 5 × 10⁻⁵ cm⁻¹) and high signal-to-noise (>3500:1) mid-infrared spectrometer based on difference-frequency infrared generation in AgGaS₂. In the low-pressure range (1-11 torr) we obtained accurate values for the line strengths, the broadening coefficients, the weak mixing coefficients, and the overall shifting of the branch. The medium pressure results, ranging from 23 to 130 torr, were analyzed by treating the band as a whole, using a relaxation matrix formalism, based on an energy gap scaling law. We find, effectively, that only 36% of the rotationally inelastic collisions are associated with Q branch mixing, the rest presumably being associated with Q-P and Q-R mixing in the same vibrational band. The pressure shifting coefficient of the 03¹0 ← 01¹0 Q branch as a whole was also determined and found to be 5.8 × 10⁻³ cm⁻¹/atm towards lower frequencies.     

Hydrogen line broadening in the ν2 and ν4 bands of phosphine at low temperature

Using a tunable diode-laser spectrometer, we have measured H₂-broadening coefficients of PH₃ at low temperature (173.2 K) for 27 lines in the ^QR branch of the ν₂ band and in the ^PP and ^RP branches of the ν₄ band. The recorded lines with J values ranging from 2 to 11 and K from 0 to 9 are located between 1016 and 1093 cm⁻¹. The collisional widths are determined by fitting each spectral line with a Voigt profile and a speed-dependent Rautian profile which provides slightly larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. Except for three ^QR(J,K) lines, where K = J, the calculated broadening coefficients are in good agreement with the experimental data. By comparing the results obtained at room and low temperatures, the temperature dependence of linewidths has been determined both theoretically and experimentally.     

N2-broadening coefficients in the ν2 and ν4 bands of PH3

N₂-broadening coefficients are measured for 61 transitions of PH₃ in the ^QR branch of the ν₂ band and the ^PP, ^RP, ^SP, and ^PQ branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 16 and K from 0 to 11 are located between 1008 and 1106 cm⁻¹. The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter models provide larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to the electrostatic contributions. The theoretical results are in good agreement with the experimental data and reproduce the J dependence of the broadenings, but their decrease at high J values is overestimated for the ^QR (J, K) transitions.     

Pressure broadening coefficients of transitions in the ν5 band of methyl bromide from fitting to Voigt and Galatry line profiles

Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v₅ fundamental band of methyl bromide (¹²CH₃⁷⁹Br and ¹²CH₃⁸¹Br) around 6.9 μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the ^RQ₁, ^PQ₃, ^PQ₅, ^PQ₇ and ^PQ₈ branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15 Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300 Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14 cm⁻¹ atm⁻¹ at low J to 0.09 cm⁻¹ atm⁻¹ at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16 cm⁻¹ atm⁻¹ with a similar J dependence to the foreign gas broadening for J > 20. However, between J = 2 and J ≈ 20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines.     

Broadening of the R(0) and P(2) lines in the CO fundamental by helium atoms from 300 K down to 12 K: Measurements and comparison with close-coupling calculations

We present measurements of He-broadening parameters for the R(0) and P(2) lines in the fundamental band of ¹³CO at different temperatures between 12 K and room temperature. The broadening parameters are determined, taking into account confinement narrowing, by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The pressure broadening cross sections are deduced and compared to close-coupling calculations and earlier results obtained for rotational transitions of ¹²CO.     

Argon broadening of the CO R(0) and R(7) transitions in the fundamental band at temperatures between 80 and 297 K: comparison between experiment and theory

We present measurements of Ar-broadening parameters for the R(0) and R(7) lines in the fundamental band of ¹³CO at eight temperatures from 80 to 297 K. The broadening parameters are determined by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The comparison of the broadening parameter values for R(7) derived at room temperature and different pressures from different line profiles shows that an empirical line profile, which takes into account narrowing effects (Dicke narrowing and absorber speed dependence) but neglects any correlation between collisions, is able to describe the observed lines with constant values of the narrowing and broadening parameters over a 10-500 Torr pressure range. Starting from a recent ab initio potential energy surface, theoretical thermally averaged close coupling values of the Ar broadening parameter are calculated for the same temperatures. The comparison between experimental and calculated values shows an overall agreement of 1.5%.     

Ar-Broadening of isotropic Raman lines in the ν2 band of acetylene

Using a high resolution Raman spectrometer, we have measured Ar-broadening coefficients in the ν₂Q branch of C₂H₂ for 22 lines at 295 K, 20 lines at 174 K, and 16 lines at 134 K. These lines with J values ranging from 1 to 23 are located in the spectral range 1970.9-1974.3 cm⁻¹. The collisional widths are obtained by fitting each spectral line with a Rautian profile. The resulting broadening coefficients are compared with theoretical values arising from close coupling and coupled states calculations. A satisfactory agreement is obtained at room as well as at low temperatures, especially for odd J lines. By comparing broadening coefficients at 295, 174, and 134 K from a simple power law, the temperature dependence of these broadenings has been determined both experimentally, and theoretically.     

Multispectrum fits for line mixing in the ν3 band Q branch of methane

First-order line-mixing coefficients and model relaxation matrix element scaling factors have been obtained for allowed transitions in the ν₃ band Q branch of CH₄ broadened by H₂, He, N₂, O₂, Ar, and CH₄. The broadening, shifting, Dicke-narrowing, and line-mixing parameters are determined by simultaneous least-squares fitting of spectra at pressures from 0.014 to 66.66 kPa recorded with a high-resolution difference-frequency laser. These results confirm, improve, and extend a previous analysis of the lower pressure (?13.3 kPa) data [A.S. Pine, J. Chem. Phys. 97 (1992) 773] which yielded averaged coefficients of individually fit spectra where adjacent broadened lines are still partially resolved.     

Q branches in the rotational spectrum of HOC1

We have obtained the far-i.r. rotational spectrm of HOCI from 70–263 cm^?1. The most prominent features of the rotational spectrum are the Q branches, for which we have measured positions. Statistical strengths for the Q branches ave been calculated and μβ, the component of the dipole moment that allows Q branch transitions has been determined from P and R branch line intensities. We find μβ = 1.4 ± 0.2 D. We also calculate Q branch strengths and shifts at stratospheric temperature.     

Illumination dependence of I-V and C-V characterization of Au/InSb/InP(1 0 0) Schottky structure

The effects of surface preparation and illumination on electric parameters of Au/InSb/InP(100) Schottky diode were investigated, in the later diode InSb forms a fine restructuration layer allowing to block In atoms migration to surface. In order to study the electric characteristics under illumination, we make use of an He-Ne laser of 1 mW power and 632.8 nm wavelength. The current-voltage I(V_G), the capacitance-voltage C(V_G) measurements were plotted and analysed. The saturation current I_s, the serial resistance R_s and the mean ideality factor n are, respectively, equal to 2.03 × 10⁻⁵ A, 85 Ω, 1.7 under dark and to 3.97 × 10⁻⁵ A, 67 Ω, 1.59 under illumination. The analysis of I(V_G) and C(V_G) characteristics allows us to determine the mean interfacial state density N_ss and the transmission coefficient θ_n equal, respectively, to 4.33 × 10¹² eV⁻¹ cm⁻², 4.08 × 10⁻³ under dark and 3.79 × 10¹² eV⁻¹ cm⁻² and 5.65 × 10⁻³ under illumination. The deep discrete donor levels presence in the semiconductor bulk under dark and under illumination are responsible for the non-linearity of the C⁻²(V_G) characteristic.     

N2- and O2-broadening of CO2 for the (301)III ← (000) band at 6231 cm

The N₂- and O₂-broadening effect have been investigated for 10 absorption lines of the CO₂ (30⁰1)_III ← (00⁰0) band centered at 6231 cm⁻¹, in the range from P(28) to R(28) by a near-infrared diode-laser spectrometer. We have analyzed the observed line profiles with the Galatry function, and determined the N₂- and O₂-broadening coefficients precisely. The air-broadening coefficients for these lines have been derived. The present results are compared with those of the previous studies for this band and with some of the other bands.     

N2-broadening coefficients in the ν2 and ν4 bands of PH3 at low temperature

N₂-broadening coefficients have been measured for 41 transitions of PH₃ at −100 °C in the ^QR branch of the ν₂ band and the ^PP, ^RP, and ^SP branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 13 and K from 0 to 10 are located between 1026 and 1093 cm⁻¹. The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter models provide larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to the electrostatic contributions. By comparing broadening coefficients at room and low temperatures, the temperature dependence of these broadenings has been determined both experimentally and theoretically.     

Self-broadening coefficients and absolute line intensities in the ν4 + ν5 band of acetylene

Self-broadening coefficients and line strengths have been measured at room temperature for 30 lines of C₂H₂ in the P and R branches of the ν₄ + ν₅ band, using a tunable diode laser spectrometer. These lines, ranging from P(22) to R(23), are located in the spectral range 1275-1390 cm⁻¹. A semiclassical calculation of the line broadenings has been performed considering the main electrostatic interactions and an anisotropic dispersion contribution leading to results in satisfactory agreement with the experimental data.     

Measurements and theoretical calculations of N2-broadening and N2-shift coefficients in the ν2 band of CH3D

In this paper, we report measured Lorentz N₂-broadening and N₂-induced pressure-shift coefficients of CH₃D in the ν₂ fundamental band using a multispectrum fitting technique. These measurements were made by analyzing 11 laboratory absorption spectra recorded at 0.0056 cm⁻¹ resolution using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. The spectra were obtained using two absorption cells with path lengths of 10.2 and 25 cm. The total sample pressures ranged from 0.98 to 402.25 Torr with CH₃D volume mixing ratios of 0.01 in nitrogen. We have been able to determine the N₂ pressure-broadening coefficients of 368 ν₂ transitions with quantum numbers as high as J″ = 20 and K = 16, where K″ = K′ ≡ K (for a parallel band). The measured N₂-broadening coefficients range from 0.0248 to 0.0742 cm⁻¹ atm⁻¹ at 296 K. All the measured pressure-shifts are negative. The reported N₂-induced pressure-shift coefficients vary from about −0.0003 to −0.0094 cm⁻¹ atm⁻¹. We have examined the dependence of the measured broadening and shift parameters on the J″, and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = −J″, J″, and J″ + 1 in the ^QP-, ^QQ-, and ^QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 4.7%. The N₂-broadening and pressure-shift coefficients were calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addition to the electrostatic contributions the atom-atom Lennard-Jones potential. The theoretical results of the broadening coefficients are in good overall agreement with the experimental data (8.7%). The N₂-pressure shifts whose vibrational contribution is derived from parameters fitted in the ^QQ-branch of self-induced shifts of CH₃D, are also in reasonable agreement with the scattered experimental data (20% in most cases).     

Measurements and theoretical calculations of self-broadening and self-shift coefficients in the ν2 band of CH3D

In this paper, we report measured Lorentz self-broadening and self-induced pressure-shift coefficients of ¹²CH₃D in the ν₂ fundamental band (ν₀ ≈ 2200 cm⁻¹). The multispectrum fitting technique allowed us to analyze simultaneously seven self-broadened absorption spectra. All spectra were recorded at the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak, AZ with an unapodized resolution of 0.0056 cm⁻¹. Low-pressure (0.98-2.95 Torr) as well as high-pressure (17.5-303 Torr) spectra of ¹²C-enriched CH₃D were recorded at room temperature to determine the pressure-broadening coefficients of 408 ν₂ transitions with quantum numbers as high as J″ = 21 and K = 18, where K″ = K′ ≡ K (for a parallel band). The measured self-broadening coefficients range from 0.0349 to 0.0896 cm⁻¹ atm⁻¹ at 296 K. All the measured pressure-shifts are negative. The reported pressure-induced self-shift coefficients vary from about −0.004 to −0.008 cm⁻¹ atm⁻¹. We have examined the dependence of the measured broadening and shift parameters on the J″, and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = −J″, J″, and J″ + 1 in the ^QP-, ^QQ-, and ^QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 3.6%. A semiclassical theory based upon the Robert-Bonamy formalism of interacting linear molecules has been used to calculate these self-broadening and self-induced pressure-shift coefficients. In addition to the electrostatic interactions involving the octopole and hexadecapole moments of CH₃D, the intermolecular potential includes also an atom-atom Lennard-Jones model. For low K (K ? 3) with |m| ? 8 the theoretical results of the broadening coefficients are in overall good agreement (3.0%) with the experimental data. For transitions with K approaching |m|, they are generally significantly underestimated (8.8%). The theoretical self-induced pressure shifts, whose vibrational contribution is derived from results in the ^QQ-branch, are generally smaller in magnitude than the experimental data in the ^QP-, and ^QR-branches (15.2%).     

Atom geometry of nanostructured Fe films grown on c(2 × 2)-N/Cu(1 0 0) surface: An investigation by X-ray absorption spectroscopy with multishell analysis

We investigated the growth of Fe nanostructured films on c(2 × 2)-N/Cu(1 0 0) surface with Fe K-edge X-ray absorption fine structure (XAFS) in the near edge and in the extended energy region. The high photon flux of the incident X-rays allowed us to perform multishell analysis of the XAFS oscillations for Fe coverage Θ_Fe < 1 ML. This data analysis yields a detailed investigation of the atom geometry and some insights in the film morphology. At Θ_N < 0.5 ML (N saturation coverage) there is absence of contribution to XAFS from N atoms. First shell analysis of linearly polarized XAFS gives Fe-Fe (or Fe-Cu) bond length values varying between R₁ = 2.526 ± 0.006 Å at the highest Fe coverage (3 ML ) and R₁ = 2.58 ± 0.01 Å at Θ_Fe = 0.5 ML, Θ_N = 0.3 ML, with incidence angle Θ = 35°. These values are different from the case of bcc Fe (R = 2.48 Å), and compatible with fcc Fe (R₁ = 2.52 Å) and fcc Cu (R₁ = 2.55 Å). At the Fe lowest coverage (Θ_Fe = 0.5 ML) the dependence of R₁ on the incidence angle indicates expansion of the outmost layer. Near edge spectra and multishell analysis can be well reproduced by fcc geometry with high degree of static disorder. At N saturation pre-coverage (Θ_N = 0.5 ML) the XAFS analysis has to keep into account the Fe-N bonding. The results suggest two different adsorption sites: one with Fe in a fcc hollow site, surrounded by other metal atoms as nearest neighbours, and one resulting from an exchange with a Cu atom underneath the N layer.     

Helium- and argon-broadening coefficients of phosphine lines in the ν2 and ν4 bands

Pressure broadening of phosphine lines by helium and argon at room temperature has been experimentally investigated by high-resolution diode-laser spectroscopy. The broadening coefficients are measured for 38 transitions of PH₃ in the ^QR branch of the ν₂ band and in the ^PP and ^RP branches of the ν₄ band. The recorded lines with J values ranging from 3 to 14 and K from 0 to 10 are located between 1062 and 1094 cm⁻¹. The retrieval of the collisional widths is carried out by fitting each spectral line with a Voigt profile, a Rautian profile and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. They are also calculated on the basis of a semiclassical model involving the atom-atom Lennard-Jones potential. The theoretical results are in reasonable agreement with the experimental data and reproduce the J and K dependencies of the broadenings.     

Room-temperature broadening and pressure-shift coefficients in the ν2 band of CH3D-O2: Measurements and semi-classical calculations

We report measured Lorentz O₂-broadening and O₂-induced pressure-shift coefficients of CH₃D in the ν₂ fundamental band. Using a multispectrum fitting technique we have analyzed 11 laboratory absorption spectra recorded at 0.011 cm⁻¹ resolution using the McMath-Pierce Fourier transform spectrometer, Kitt Peak, Arizona. Two absorption cells with path lengths of 10.2 and 25 cm were used to record the spectra. The total sample pressures ranged from 0.98 to 339.85 Torr with CH₃D volume mixing ratios of 0.012 in oxygen. We report measurements for O₂ pressure-broadening coefficients of 320 ν₂ transitions with quantum numbers as high as J″ = 17 and K = 14, where K″ = K′ ≡ K (for a parallel band). The measured O₂-broadening coefficients range from 0.0153 to 0.0645 cm⁻¹ atm⁻¹ at 296 K. All the measured pressure-shifts are negative. The reported O₂-induced pressure-shift coefficients vary from about −0.0017 to −0.0068 cm⁻¹ atm⁻¹. We have examined the dependence of the measured broadening and shift parameters on the J″, and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = −J″, J″, and J″ + 1 in the ^QP-, ^QQ-, and ^QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 4.4%. The O₂-broadening and pressure shift coefficients were calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addition to the electrostatic contributions the atom-atom Lennard-Jones potential. The theoretical results of the broadening coefficients are generally larger than the experimental data. Using for the trajectory model an isotropic Lennard-Jones potential derived from molecular parameters instead of the spherical average of the atom-atom model, a better agreement is obtained with these data, especially for |m| ? 12 values (11.3% for the first calculation and 8.1% for the second calculation). The O₂-pressure shifts whose vibrational contribution are either derived from parameters fitted in the ^QQ-branch of self-induced shifts of CH₃D or those obtained from pressure shifts induced by Xe in the ν₃ band of CH₃D are in reasonable agreement with the scattered experimental data (17.0% for the first calculation and 18.7% for the second calculation).     

Spectral line parameters in the (3 ← 0) overtone band of the HI molecule and line-mixing in the band head

The linestrengths, self-pressure broadening and shifting coefficients have been measured for P₃ (10)- R₃ (12) lines in the second overtone band of hydrogen iodide. A dipole moment function in terms of the reduced nuclear displacement x = (R − R_e)/R_e is obtained using rotationless dipole matrix elements determined by the Herman-Wallis analysis of the (1, 2, 3 ← 0) HI bands: μ (x) = 0.4471(5) − 0.0770(2)x + 0.547(3)x² − 1.93(2)x³, in a full agreement with the function proposed previously [J. Mol. Spectrosc. 223 (2004) 67]. A close match is demonstrated of the results of most recent relativistic calculations [Phys. Chem. Chem. Phys. 6 (2004) 3779] with the spectroscopically derived electric dipole parameters for HI. Line-mixing in the band head is observed, the self-pressure shifting and broadening coefficients for the (3 ← 0) band lines are determined.     

NaK bound-free and bound-bound 4 Σ → aΣ emission

The relative transition dipole moment function M(R) for the 4 ³Σ⁺ → a³Σ⁺ electronic transition in the sodium-potassium molecule (NaK) has been determined by fitting experimental bound-free and bound-bound emission spectra. The fit is performed using a modified version of the BCONT computer program, which was originally developed by Le Roy. Spectra previously measured in this laboratory from low-lying ro-vibrational levels of the 4 ³Σ⁺ state and new spectra from high-lying levels are included in the fit. A slight adjustment to the inner, repulsive wall of the 4 ³Σ⁺ potential leads to an improved form for that curve. The fitted M(R), when appropriately scaled, agrees very well with recent ab initio calculations of Magnier et al.