High-resolution Infrared Emission Spectra Research Articles

Multi-isotopologue analyses of new vibration–rotation and pure rotation spectra of ZnH and CdH

High resolution infrared emission spectra of ZnH, ZnD, CdH, and CdD have been recorded with a Fourier transform spectrometer. The v = 1 → 0 and v = 2 → 1 bands of ZnH, ZnD, CdH, and CdD, as well as the v = 3 → 2 band of ZnD were observed for the X 2Σ + ground electronic state. In addition, new rotational spectra have been recorded for CdH and CdD using a tunable far-infrared spectrometer, and pure rotational transitions in the v = 1 level of the ground state were measured. The new data were combined with the previous data from diode laser infrared spectra and pure rotation spectra of ZnH/ZnD and CdH/CdD available in the literature. The data from all isotopologues were fitted together using a Dunham-type energy level expression for 2Σ + states, and Born–Oppenheimer breakdown correction parameters were obtained. The equilibrium rotational constants ( B e) of 64ZnH, 64ZnD, 114CdH, and 114CdD were determined to be 6.691332(17), 3.402156(7), 5.447074(18), and 2.750761(6) cm −1, respectively, and the associated equilibrium internuclear distances ( r e) are 1.593478(2), 1.593001(2), 1.760098(3), and 1.759695(2) Å, respectively. Simple reduced mass scaling for the spin–rotation interaction constants of ZnH and CdH fully accounted for their isotopologue dependence, and no Born–Oppenheimer breakdown correction was required for these parameters.

Gaseous HgH2, CdH2, and ZnH2.

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Infrared Emission Spectra and Equilibrium Structures of Gaseous HgH2 and HgD2

A detailed analysis of the high-resolution infrared emission spectra of gaseous HgH2 and HgD2 in the 1200-2200 cm(-1) spectral range is presented. The nu3 antisymmetric stretching fundamental bands of 204HgH2, 202HgH2, 201HgH2, 200HgH2, 199HgH2, 198HgH2, 204HgD2, 202HgD2, 201HgD2, 200HgD2, 199HgD2, and 198HgD2, as well as a few hot bands involving nu1, nu2, and nu3 were analyzed rotationally, and spectroscopic constants were obtained. Using the rotational constants of the 000, 100, 01(1)0, and 001 vibrational levels, we determined the equilibrium rotational constants (B(e)) of the most abundant isotopologues, 202HgH2 and 202HgD2, to be 3.135325(24) cm(-1) and 1.569037(16) cm(-1), respectively, and the associated equilibrium Hg-H and Hg-D internuclear distances (re) are 1.63324(1) A and 1.63315(1) A, respectively. The re distances of 202HgH2 and 202HgD2 differ by about 0.005%, which can be attributed to the breakdown of the Born-Oppenheimer approximation.

The vibration-rotation emission spectrum of hot BeF2

The high-resolution infrared emission spectrum of BeF2 vapor at 1000 degrees C was rotationally analyzed with the assistance of large-scale ab initio calculations using the coupled-cluster method including single and double excitations and perturbative inclusion of triple excitations, in conjunction with correlation-consistent basis sets up to quintuple-zeta quality. The nu3 fundamental band, the nu1+nu2, nu1+nu3, and 2nu2+nu3 combination bands, and 18 hot bands were assigned. The symmetric stretching (nu1), bending (nu2), and antisymmetric stretching (nu3) mode frequencies were determined to be 769.0943(2), 342.6145(3), and 1555.0480(1) cm-1, respectively, from the band origins of the nu3, nu1+nu3, and nu1+nu2 bands. The observed vibrational term values and B rotational constants were fitted simultaneously to an effective Hamiltonian model with Fermi resonance taken into account, and deperturbed equilibrium vibrational and rotational constants were obtained for BeF2. The equilibrium rotational constant (Be) was determined to be 0.235 354(41) cm-1, and the associated equilibrium bond distance (re) is 1.3730(1) A. The results of our ab initio calculations are in remarkably good agreement with those of our experiment, and the calculated value was 1.374 A for the equilibrium bond distance (re). As in the isoelectronic CO2 molecule, the Fermi resonance in BeF2 is very strong, and the interaction constant k122 was found to be 90.20(4) cm-1.

Gaseous HgH2, CdH2, and ZnH2

Gaseous HgH2, CdH2, and ZnH2 molecules were synthesized by the direct gas-phase reaction of excited mercury, cadmium, and zinc atoms with molecular hydrogen. The molecules were identified by their high-resolution infrared emission spectra, and the metal-hydrogen bond lengths were determined from the rotational analysis of the antisymmetric stretching fundamental bands.

Sensitivity Analysis of Cirrus Cloud Properties from High-Resolution Infrared Spectra. Part I: Methodology and Synthetic Cirrus

AbstractA set of simulated high-resolution infrared (IR) emission spectra of synthetic cirrus clouds is used to perform a sensitivity analysis of top-of-atmosphere (TOA) radiance to cloud parameters. Principal component analysis (PCA) is applied to assess the variability of radiance across the spectrum with respect to microphysical and bulk cloud quantities. These quantities include particle shape, effective radius (reff), ice water path (IWP), cloud height Zcld and thickness ΔZcld, and vertical profiles of temperature T(z) and water vapor mixing ratio w(z). It is shown that IWP variations in simulated cloud cover dominate TOA radiance variability. Cloud height and thickness, as well as T(z) variations, also contribute to considerable TOA radiance variability.The empirical orthogonal functions (EOFs) of radiance variability show both similarities and differences in spectral shape and magnitude of variability when one physical quantity or another is being modified. In certain cases, it is possible to identify the EOF that represents variability with respect to one or more physical quantities. In other instances, similar EOFs result from different sets of physical quantities, emphasizing the need for multiple, independent data sources to retrieve cloud parameters. When analyzing a set of simulated spectra that include joint variations of IWP, reff, and w(z) across a realistic range of values, the first two EOFs capture approximately 92%–97% and 2%–6% of the total variance, respectively; they reflect the combined effect of IWP and reff. The third EOF accounts for only 1%–2% of the variance and resembles the EOF from analysis of spectra where only w(z) changes. Sensitivity with respect to particle size increases significantly for reff several tens of microns or less. For small-particle reff, the sensitivity with respect to the joint variation of IWP, reff, and w(z) is well approximated by the sum of the sensitivities with respect to variations in each of three quantities separately.

Vibration−Rotation Emission Spectra of Gaseous ZnH2 and ZnD2

Gaseous ZnH2 and ZnD2 have been discovered in an emission source that combines an electrical discharge with a high-temperature furnace. High-resolution infrared emission spectra of ZnH2 and ZnD2 have been recorded with a Fourier transform spectrometer, and the antisymmetric stretching fundamental bands of 64ZnH2 and 64ZnD2 were detected near 1889.4 and 1371.6 cm-1, respectively. Rotational analysis of the bands yielded r0 bond distances of 1.535 271(1) and 1.531 836(9) A for linear 64ZnH2 and 64ZnD2, respectively.

The antisymmetric stretching fundamental band of free MgD2

The gaseous MgD2 molecule has been synthesized for the first time in an electrical discharge inside a high-temperature furnace. The high-resolution infrared emission spectrum of MgD2 was recorded with a Fourier transform spectrometer, and the antisymmetric stretching mode (v3) was detected near 1176.5 cm–1. The v3 band was rotationally analyzed, and the r0 Mg—D bond distance was determined to be 1.700 874(8) Å.Key words: gaseous MgD2, vibration-rotation emission spectrum, Mg-D bond distance.

Infrared emission spectra of BeH2 and BeD2

High resolution infrared emission spectra of beryllium dihydride and dideuteride have been recorded with a Fourier transform spectrometer. The molecules were generated in a discharge-furnace source, at 1500 °C and 333 mA discharge current, with beryllium metal and a mixture of helium and hydrogen or deuterium gases. The antisymmetric stretching modes (ν3) of BeH2 and BeD2, as well as several hot bands involving ν1, ν2, and ν3, were rotationally analyzed and spectroscopic constants were determined. The equilibrium rotational constant (Be) of BeH2 was found to be 4.753 66(2) cm−1, and the equilibrium bond distance (Re) of 1.326 407(3) Å was determined for BeH2.

Infrared emission spectra of BeH and BeD

High resolution infrared emission spectra of beryllium monohydride and monodeuteride have been recorded. The molecules were generated in a furnace-discharge source, at 1500 °C and 333 mA discharge current, with beryllium metal and a mixture of helium and hydrogen or deuterium gases. Approximately 160 BeH lines and 167 BeD lines for the vibrational bands v=1→0 to v=4→3 were observed in the spectra and spectroscopic constants were determined. The Dunham constants (Yl,m) and Born–Oppenheimer breakdown constants were obtained in a combined fit of the BeH and BeD data. The equilibrium rotational constants (Be) for BeH and BeD were found to be 10.319 59(3) cm−1 and 5.688 29(2) cm−1, respectively, while the equilibrium vibrational constants (ωe) are 2061.416(3) and 1529.956(3) cm−1. The equilibrium distance (Re) was determined to be 1.342 436(2) Å for BeH.

Vibration-rotation emission spectra and combined isotopomer analyses for the coinage metal hydrides: CuH & CuD, AgH & AgD, and AuH & AuD

High resolution infrared emission spectra have been measured for AuH and AuD and for two isotopomers of each of CuH, CuD, AgH, and AgD. The molecules were made in a carbon tube furnace (King furnace), and in spite of intense background thermal emission from the furnace (at >2000 °C), vibration–rotation emission data could be recorded. Together with high resolution measurements taken from the literature, the data for each species were treated using two types of combined-isotopomer analysis: One based on fits to empirical molecular parameters, and the other based on direct fits to the underlying potential energy functions, both of which take account of mass-dependent Born–Oppenheimer breakdown correction terms. Accurate isotopically related Dunham parameters and Born–Oppenheimer breakdown parameters are obtained for each species, as well as accurate analytic potential functions and adiabatic and nonadiabatic radial correction functions.

High resolution Fourier transform infrared emission spectra of lithium iodide

The high resolution infrared emission spectrum of lithium iodide has been recorded with a Fourier transform spectrometer. A total of 1024 transmissions with Δ v = 1 for 7 LiI (from v = 1 → 0 to v = 8 → 7), 387 transitions with Δ v = 2(v = 2 → 0 to v = 6 → 4) and 504 transitions with Δ v = 1 for 6 LiI (v = 1 → 0 to v = 5 → 4) have been assigned. The infrared data have been used to determine improved mass-dependent Dunham Y lm coefficients for the ground X1 Σ+ electronic state. The mass-independent Dunham U lm coefficients were obtained along with Born-Oppenheimer breakdown constants. Finally, all of the data were fitted to the eigenvalues of the radial Schrodinger equation containing a modified Morse potential function to determine the parameters of an effective ground state potential.)

High resolution Fourier transform infrared emission spectra of lithium iodide

The high resolution infrared emission spectrum of lithium iodide has been recorded with a Fourier transform spectrometer. A total of 1024 transmissions with Δ v = 1 for 7 LiI (from v = 1 → 0 to v = 8 → 7), 387 transitions with Δ v = 2(v = 2 → 0 to v = 6 → 4) and 504 transitions with Δ v = 1 for 6 LiI (v = 1 → 0 to v = 5 → 4) have been assigned. The infrared data have been used to determine improved mass-dependent Dunham Y lm coefficients for the ground X1 Σ+ electronic state. The mass-independent Dunham U lm coefficients were obtained along with Born-Oppenheimer breakdown constants. Finally, all of the data were fitted to the eigenvalues of the radial Schrödinger equation containing a modified Morse potential function to determine the parameters of an effective ground state potential.)

Infrared Emission Spectrum of KF

The high-resolution infrared emission spectrum of potassium monofluoride has been recorded with a Fourier transform spectrometer. Over 900 vibration–rotation transitions, from thev= 1 → 0 to thev= 8 → 7 vibrational bands, have been assigned. Improved spectroscopic constants have been obtained for the KF ground electronic state by combining the infrared measurements with the existing microwave data.

High-Resolution Infrared Emission Spectrum of NaF

The high-resolution infrared emission spectrum of sodium monofluoride has been recorded with a Fourier transform spectrometer. A total of 1131 of vibration–rotation transitions, from thev= 1 → 0 tov= 9 → 8 vibrational bands, have been assigned. The infrared data have been combined with existing microwave data in order to obtain improved spectroscopic constants, including DunhamYijandUijcoefficients, for theX1Σ+electronic ground state of NaF.

High-Resolution Infrared Emission Spectrum of CaF

The high-resolution infrared emission spectrum of calcium monofluoride has been observed with a Fourier transform spectrometer. A total of 790 rovibrational transitions, from the ν = 1 → 0 to ν = 8 → 7 bands have been assigned. This set of infrared data has been combined with existing microwave data to yield improved Dunham Yij coefficients for the X2Σ+ electronic ground state of CaF.

High-Resolution Fourier Transform Infrared Emission Spectra of Barium Monofluoride

The high-resolution infrared emission spectra of gas-phase barium monofluoride have been observed by Fourier transform spectrometry. Vibration-rotation bands were analyzed for the three most abundant isotopomers (138BaF, from 1-0 to 12-11; 137BaF, from 1-0 to 5-4; 136BaF, from 1-0 to 4-3) of the ground X2Σ+ state. The Dunham coefficients, Ylm, have been derived for all three isotopomers by fitting about 1750 lines for 138BaF, about 270 lines for 137BaF, and about 70 lines for 136BaF to the traditional Dunham model. In addition, the mass-reduced Dunham constants, Ulm, have been calculated from a global least-squares fit.

Infrared Emission Spectroscopy of BF and AlF

The high-resolution infrared emission spectrum of boron monofluoride was recorded with a Fourier transform spectrometer. There are 359 transitions of 11BF with ν = 1 → 0 to ν = 5 → 4, and 94 transitions of 10BF with ν = 1 → 0 to ν = 3 → 2 assigned. Improved Dunham Yij coefficients for the ground X1Σ+ electronic state were determined from the infrared data combined with existing microwave data. The mass-reduced Dunham Uij coefficients were also obtained along with Born-Oppenheimer breakdown constants. An effective Born-Oppenheimer potential was determined by fitting the available data to the eigenvalues of the radial Schrödinger equation containing a parameterized potential function. Finally, the relative transition dipole moments of the major isotopomer 11BF were also measured. For AlF, our previous measurements were extended to higher ν and J, in order to obtain improved Dunham coefficients and an improved internuclear potential.

Vibration-Rotation Emission Spectrum of MgF

The high-resolution infrared emission spectrum of MgF was recorded with a Fourier transform spectrometer. More than 800 rovibrational lines from the ν = 1 → 0 to ν = 7 → 6 bands were assigned. The Dunham coefficients for the X 2Σ + electronic ground state were obtained.

Infrared Emission Spectra of InH and InD

High-resolution infrared emission spectra of diatomic indium hydride and deuteride were recorded with a Fourier transform spectrometer. A total of 377 InH lines from the (1, 0) to (5, 4) bands and 257 InD lines from the (1,0) to (4, 3) bands were measured. Revised sets of isotopically dependent Dunham Y constants and isotopically invariant Dunham U constants for the X 1Σ + ground state were determined. In addition, a parametrized internuclear potential for the X 1Σ + state was also obtained from a direct fit of the data to the eigenvalues of the radial Schrödinger equation.