High resolution spectroscopy of the nu(3) band of DCOOD

The rotation-vibration spectrum of DCOOD has been recorded in the carbonyl stretch (nu(3)) region. Using a standard S-reduced Watson Hamiltonian in the I(r) representation, 225 lines could be fitted to a vibrational-rotational band. A full set of molecular constants was obtained. The nu(3) band is found to be strongly perturbed in the K(a): 1<--1 and K(a): 2<--2 subband. The perturbation is attributed to a Fermi resonance with the 2nu(8) overtone band and Coriolis coupling to a combination band (nu(4)+nu(7)). The band center is determined to be 1725.1218(1) cm(-1) which is more than 10 cm(-1) shifted compared to previous studies.     

High resolution FTIR measurements of LVM-structure in GaAs

High resolution measurements of LVMs (localised vibrational modes) can give vital information about the configuration of defects within a crystal lattice. Illustrations of this technique for the centres B_As, B(1) and Si_Ga-Ge_As in GaAs are presented.     

High resolution vacuum ultraviolet emission spectrum of D2: the B' 1Sigmau+-->X 1Sigmag+ band system

In this work, we have extended our previous high resolution study of the vacuum ultraviolet emission spectrum of the D2 molecule [M. Roudjane, et al. J. Chem. Phys. 125, 214305 (2006)] up to 124.2 nm in order to investigate the B' 1Sigmau+-->X 1Sigmag+ band system. The analysis of the spectrum has been carried out by means of a complex spectrum visual identification code IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656, (1993)] and supported by theoretical calculations using ab initio data [L. Wolniewicz, J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); G. Staszewska and L. Wolniewicz, J. Mol. Spectrosc. 212, 208 (2002); L. Wolniewicz and G. Staszewska, 220, 45 (2003)] which provided level energies and transition probabilities. More than 1480 new emission lines have been observed and 109 bands belonging to the B' 1Sigmau+-->X 1Sigmag+ system have been identified between 84.1 and 121.6 nm. Except for the upsilon'-0 bands that were reported in absorption [I. Dabrowski and G. Herzberg, Can. J. Phys. 52, 1110 (1974)], all the upsilon'-upsilon" bands are reported here for the first time. The analysis led to the determination of 111 rovibronic energy levels in the B' 1Sigmau+ state, of which 31 with higher rotational numbers J are new. Observed perturbations are accounted for through a set of coupled equations involving the four excited electronic states B 1Sigmau+, B' 1Sigmau+, C 1Piu, and D 1Piu and including nonadiabatic couplings. The solution of this set provides the percent contribution of these four states to each of the observed rovibronic level.     

High resolution absorption spectrum of dianilino in the vapor phase

Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz. And this absorption band also used as wavelength calibration for all the photoproducts formed in the reaction cell during optical pumping.     

High resolution FT-IR spectrum of tricarbon bisulfide,SCCCS

The high resolution Fourier transform infrared spectra of thev ₄-v ₂ andv ₇ band systems of tricarbon disulfide, SCCCS, were measured with a Bomem D A3.002 interferometer and an apodized resolution of 0.004 cm^–1. The rotational structure of the bandsv ₄-v ₂, (v ₄+v ₇)–(v ₂+v ₇), (v ₄+2v ₇)–(v ₂+2v ₇) andv ₇ could be resolved and assigned. The analysis confirmed that SCCCS displays the dynamics of a linear molecule.     

High resolution infrared spectrum and molecular structure of dichloroacetylene

The infrared spectrum of dichloroacetylene, prepared by the pyrolysis of dichloromaleic anhydride at 1000°C, has been recorded at both low and high resolution. In the low resolution spectrum a number of combination bands not previously observed have been assigned, the infrared active fundamentals have been reassigned, and a center wavenumber value has been determined for the Raman activev ₁ fundamental. The high resolution spectra of a number of fundamental bands, summation bands, and one difference band for the isotopomers,³⁵CICC³⁵CI and³⁵CICC³⁷CI, have been assigned, while a more limited number of bands has been assigned for the species³⁷CICC³⁷CI and³⁵CI¹³CC³⁵CI. The resultant rotational and vibration-rotation constants have been used to obtainr _o,r _e,r _s, and partial r_s structural parameters. The most reliable bond lengths are obtained from the partialr _s treatment and are 164.105(53) pm for the C-CI bond and 119.203(79) pm for the CC bond.     

High resolution study of the γ-ray spectrum following228Ac decay

The decay of²²⁸Ac has been reinvestigated by means of high resolution HPGe detectors. Accurate energies and intensities of 242 photons were measured, of which 80 were found for the first time.     

High resolution infrared spectra and rovibrational analysis of the coupled nu2/nu5 bands of D3Si35Cl. Equilibrium rotational constants

The Fourier transform infrared spectrum of monoisotopic D3Si35Cl in the region of the nu2/nu5 band system was recorded with a resolution of 2.4x10(-3) cm-1. More than 9000 lines of the strongly Coriolis x,y-coupled bands, (nu2)0=701.936, and (nu5)0=688.898 cm-1, have been assigned, among them 276 forbidden but perturbation allowed transitions around avoided crossings according to Delta(k-l)=+/-3 mechanisms. Three different models taking into account redundancies in the framework of unitary equivalent reductions of the rovibrational Hamiltonian have been employed to fit the data. All three models reproduced consistently the full data set employing 28 refined parameters with an rms deviation of 0.31x10(-3) cm-1. The equivalence of the parameter sets was established by the agreement of parameter sums obtained with the different models. The analysis of the avoided crossings, together with the fit of the forbidden lines, allowed an independent determination of the ground state parameters A0 and D(K)0. Combined with existing data for nu1, nu3, nu4, and nu6, the present results allowed the determination of experimental values, Ae=1.4371895(94) and Be=0.19823049(59) cm-1. The experimental results are compared with those of previous ab initio calculations of the anharmonic force field.     

High resolution fourier transform infrared spectrum of difluoroethyne,FCCF.

Difluoroethyne, monitored by FTIR spectroscopy, has been prepared in the vapour phase by vacuum pyrolysis and photolysis of difluoromaleic anhydride and pyrolysis of 3-bromo-3,3-difluoropropanoic trifluoroacetic anhydride. The infrared spectrum of difluoroethyne has been assigned at both low and high resolution and wavenumber values for all five fundamentals estimated. Difluoropropadienone was observed as a pyrolysis product and difluorocyclopropenone as a photolysis product.     

Contribution of the asymmetric stretch, nu3B1, to the fundamental Raman spectrum of water

The OD-stretching overtone from liquid D2O, 2nu, and the fundamental OD stretch from dilute HDO, both display high-frequency depolarization ratio minima, but the fundamental OD stretch from neat D2O displays a maximum, at the equivalent position. The rhoL minima arises from the decreased depolarization ratio produced by the absence of B1 modes. The fundamentals of HDO are of A species, and the 2nu overtone of D2O only involves A1 species, e.g., 2nu3B1 has A1 species via B1 x B1 = A1. A and A1 modes display small rhoL values which produce minima in rhoL near 2665 cm(-1) for HDO, and near 5250 cm(-1) for the D2O overtone. These minima give way to a depolarization ratio maximum when the depolarized, rhoL = 34, nu3B1 fundamental, makes its appearance in D2O at 2650 cm(-1). Fundamental and overtone depolarization ratios were used to determine the nu3B1 contribution to the depolarization ratio of the fundamental OD stretch; a value of approximately 28% resulted at 2655 cm(-1). Liquid H2O displays completely analogous features; a value of approximately 20% resulted for it at 3660 cm(-1). Nonhydrogen-bonded nu3B1, and more strongly hydrogen-bonded nu3B1, modes are also indicated for D2O and H2O. A rigorous test of the current results can be accomplished by measuring the depolarization ratio of the extraordinarily weak second Raman overtone, 3nu, recently detected for D2O.     

High-resolution infrared spectrum of the nu1 Ba nd of eta5-C5H5NiNO

Gas-phase rotational constants and distortion constants have been determined for the nu1 (v=1) excited vibrational state of cyclopentadienylnickel nitrosyl (C5H5NiNO) using a high-resolution Fourier transform spectrometer system at Kitt Peak, Arizona. The rotationally resolved lines have been measured for the C-H symmetric stretch vibration (nu1=3110 cm(-1)). In the present analysis, over 150 lines have been assigned and fitted using a rigid-rotor Hamiltonian with centrifugal distortion. The vibrational band center, excited-state rotational constants, and distortion constants derived from the measured spectrum for this prolate symmetric-top molecule are nuo=3110.4129(4) cm(-1), A'=0.14328(8) cm(-1), B'=C'=0.041285(1) cm(-1), DJ'=0.078(1) kHz, DJK'=2.23(4) kHz, and DK'=-2.63(2) kHz, respectively. Several different combination differences, with a common upper state, were calculated for different K stacks for the observed spectra, and the consistency of the lower state rotational constants obtained provided further support for the current assignment. The ground-state rotational constant (B') derived from this combination differences analysis agrees with the previously obtained Fourier transform microwave value to within 0.15%. However, ground-state rotational constants, A' and B', have been fixed in the present analysis to avoid correlation effects and to get more accurate results. The new measured parameters are compared with the previously obtained results from Fourier transform microwave and infrared spectroscopy measurements. The C-H vibration stretching frequency and rotational constants were calculated using density functional theory calculations, and these were quite helpful in resolving ambiguities in the fitting procedure and for initial assignments of measured lines.     

High resolution proton coupled 13C spectrum and structure of butadieneiron tricarbonyl

A complete analysis of the proton coupled ¹³C spectrum of butadieneiron tricarbonyl is presented. The structure of the diene ligand is discussed on the basis of vicinal C,H and H,H coupling constants as well as ²J(HH), ¹J(CH) and ¹J(CC) data. These data are interpreted in terms of a non-planar C,H skeleton in which C,C bond lengths are nearly equal and the terminal carbon atoms exhibit some rehybridization towards sp³. The results obtained from the complex in solution agree with a structural model from X-ray data of substituted butadieneiron tricarbonyl complexes.     

Evidence for new bands in the 3nu1 and 4nu1 regions of propyne

Vibrationally mediated photodissociation and room-temperature photoacoustic (PA) spectroscopy have been used for obtaining action (monitoring the yield of H photofragments) and absorption spectra of the second (3nu(1)) and third (4nu(1)) C-H acetylenic stretches overtone regions in propyne. The band contours appearing in these regions seem mostly regular even though they are perturbed, as expressed by the origin shifts in different K components, splitting of the K structure, and splitting due to resonances between neighboring states. Symmetric rotor simulations of the band contours of the PA and action spectra allowed extraction of the molecular parameters and rough estimates for the homogeneous broadening arising from energy flow to the bath vibrational states. We particularly benefited from the reduced congestion in the jet-cooled action spectra and their simulations, which enabled observation of yet unknown features in the vicinity of the 3nu(1) and 4nu(1) states. Particularly, the emergence of the new state in the 3nu(1) region was confirmed by the action spectra monitored at several differing jet temperatures, suggesting that it is a dark state in IR vibrational excitation that becomes brighter in UV excitation to the upper electronic state. The monitored and Gaussian-fitted Doppler profiles point to the release of H photofragments with low average translational energies, attributed to an indirect dissociation process occurring after internal conversion to the ground electronic state and isomerization to allene.     

Observation and rovibrational analysis of the intermolecular NH3 libration band nu9(1) of H3N-HCN

The high-resolution far-infrared absorption spectrum of the gaseous molecular complex H(3)N-HCN is recorded by means of static gas-phase Fourier transform far-infrared spectroscopy at 247 K, using a synchrotron radiation source. The spectrum contains distinct rotational structures which are assigned to the intermolecular NH(3) libration band nu9(1) (nu(B)) of the pyramidal H(3)N-HCN complex. A rovibrational analysis based on a standard semirigid symmetric top molecule model yields the band origin of 260.03(10) cm(-1), together with values for the upper state rotational constant B' and the upper state quartic centrifugal distortion constants D'(J) and D'(JK). The values for the upper state spectroscopic constants indicate that the hydrogen bond in the H(3)N-HCN complex is destabilized by 5% and elongates by 0.010 A upon excitation of a quantum of libration of the hydrogen bond acceptor molecule.     

FTIR identification of the nu4(sigmau) and nu6(piu) modes of linear GeC3Ge trapped in solid Ar

GeC 3Ge was previously (1) produced by the dual laser ablation of germanium and carbon rods, and the nu 3(sigma u) carbon-carbon stretching fundamental was assigned at 1920.7 cm (-1). This paper presents results from new experiments that have enhanced the production of the molecule via laser ablation of a single sintered germanium-carbon rod, thus enabling the identification of two additional infrared active vibrational fundamentals. Ge participates strongly in one of these, the nu 4(sigma u) mode, and the corresponding Ge isotopic shifts reported here are the first for a germanium-carbon species. GeC 3Ge was produced by trapping the products from the laser evaporation of the Ge-C rod, in solid Ar at approximately 10 K, and recording the FTIR (Fourier transform infrared) spectra. Comparison of (70,72,73,74,76)Ge and (13)C isotopic shift measurements with the predictions of density functional theory calculations (DFT) at the B3LYP/cc-pVDZ level confirms the identification of the nu 4(sigma u) stretching fundamental at 735.3 cm (-1) and the nu 6(pi u) bending fundamental at 580.1 cm (-1) for linear GeC 3Ge.     

Absolute line intensities determination in the nu7 band of C2H4

Absolute intensities have been measured for 26 lines of C2H4 in the nu7 fundamental transition, using a tunable diode-laser spectrometer. These lines with 3< or = J"< or = 21, 2< or = Ka< or = 4, 2< or = Kc< or = 20 are located in the spectral range 920-980 cm(-1). The intensities have been measured by using two methods: the equivalent width method (EWM) and the line profile fit method (FPM). For the last one, three models have been tested: Voigt, Rautian and Galatry profiles.     

Determining the resolution of Laplace inversion spectrum

In experiments involving decaying signals, it is often desirable to analyze the data as a sum of exponential decays using the Laplace inversion method. However, Laplace inversion is an ill-conditioned problem, and it is difficult to ascertain the stability of the reconstruction method and resolution of the resulting spectrum. This paper provides an easily computed approximate bound of the resolution and offers guidelines on how to design experiments to improve the spectral resolution.     

FTIR spectrum of benzene in a supersonic expansion

The 700 and 3050 cm^?1 region of benzene seeded in argon is studied using Fourier-transform infrared absorption spectroscopy. Analysis of the sequence band structure in the 700 cm^?1 region gave new anharmonic constants and values of T_rot (79 ± 15 K) and T_vib (/2~160 K) which indicate a disequilibrium between the rotational and vibrational degrees of freedom. A band contour analysis of the 3050 cm^?1 Fermi triad is used to obtain new values of the Coriolis coupling constants and band origins.     

Absolute band intensities in the nu19/nu23 (530 cm(-1)) and nu7 (777 cm(-1)) bands of acetone ((CH3)2CO) from 232 to 295 K

Absolute band intensities of acetone ((CH3)2CO) in the nu19/nu23 and nu7 band systems near 530 and 777 cm(-1), respectively, were measured at temperatures of 232, 262 and 295 K, using a Fourier transform infrared (FTIR) spectrometer. No evident temperature dependence for the band intensities was observed. The dipole moments and the fundamental band intensities were derived in the harmonic oscillator approximation. The results are useful for the spectroscopic retrieval of acetone concentrations in the upper atmosphere.