N Bands Research Articles

Measurement of hemoglobin oxygen saturation using Raman microspectroscopy and 532-nm excitation

The resonant Raman enhancement of hemoglobin (Hb) in the Q band region allows simultaneous identification of oxy- and deoxy-Hb. The heme vibrational bands are well known at 532 nm, but the technique has never been used to determine microvascular Hb oxygen saturation (So(2)) in vivo. We implemented a system for in vivo noninvasive measurements of So(2). A laser light was focused onto areas of 15-30 microm in diameter. Using a microscope coupled to a spectrometer and a cooled detector, Raman spectra were obtained in backscattering geometry. Calibration was performed in vitro using blood at several Hb concentrations, equilibrated at various oxygen tensions. So(2) was estimated by measuring the intensity of Raman signals (peaks) in the 1,355- to 1,380-cm(-1) range (oxidation state marker band nu(4)), as well as from the nu(19) and nu(10) bands (1,500- to 1,650-cm(-1) range). In vivo observations were made in microvessels of anesthetized rats. Glass capillary path length and Hb concentration did not affect So(2) estimations from Raman spectra. The Hb Raman peaks observed in blood were consistent with earlier Raman studies using Hb solutions and isolated cells. The correlation between Raman-based So(2) estimations and So(2) measured by CO-oximetry was highly significant for nu(4), nu(10), and nu(19) bands. The method allowed So(2) determinations in all microvessel types, while diameter and erythrocyte velocity could be measured in the same vessels. Raman microspectroscopy has advantages over other techniques by providing noninvasive and reliable in vivo So(2) determinations in thin tissues, as well as in solid organs and tissues in which transillumination is not possible.

Interchange-tunneling splitting in HCl dimer in helium nanodroplets

Midinfrared spectra of HCl dimers have been obtained in helium nanodroplets. The interchange-tunneling (IT) splitting in the vibrationally excited state of the bonded H-Cl stretching band (nu(2)) in (H(35)Cl-H(37)Cl) dimers was measured to be 2.7+/-0.2 cm(-1), as compared to 3.7 cm(-1) in free dimer. From the splitting, the strength of the IT coupling in liquid helium of 0.85+/-0.15 cm(-1) was obtained, which is about a factor of 2 smaller than in the free dimer. The results are compared with the previous spectroscopic study of (HF)(2) in He droplets as well as the theoretical study of (HF)(2) and (HCl)(2) dimers in small He clusters.

Effect of nickel substitutions on some properties of Cu–Zn ferrites

Abstract The spinel ferrite system Cu0.8−xZn0.2NixFe2O4; 0.0 ≤ x ≤ 0.8 is prepared by standard ceramic method. X-ray diffraction (XRD) measurements are used for analyzing the composition, lattice parameter, density, porosity and grain size of these compounds. The infrared spectra (IR) obtained at room temperature in the range 400–4000 cm−1 showed two absorption spectra. The high-frequency band (ν1) and low-frequency band (ν2) are assigned to the tetrahedral and octahedral complexes, respectively. The electrical measurements of these ferrites at various compositions were investigated from room temperature up to 650 K in the frequency range (102–105 Hz). The obtained results revealed semiconductor behavior with an increasing nickel concentration with change in the slope at transition temperature Tc. The determined Tc is found to increase with an increasing Ni concentration. The activation energies calculated at the magnetic region are found to decrease with an increasing Ni content. The relation of the universal exponent s with temperature gives evidence for the presence of the large overlap polaron (LOP) hopping conduction mechanism in these compounds. The obtained results of conductivity are explained in light of the hopping conduction occurring at the octahedral B-sites.

High-resolution infrared and theoretical study of the fundamental bands ν2, ν4 and ν9 and the c-Coriolis interacting dyad ν5, ν14 of 1,3,4-thiadiazole

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C 2H 2N 2S, has been recorded with a resolution of ca. 0.003 cm −1 in the 800–1500 cm −1 spectral region. Five fundamental bands ν 2(A 1; 1391.9 cm −1), ν 4(A 1; 964.4 cm −1), ν 5(A 1; 894.6 cm −1), ν 9(B 1; 821.5 cm −1), and ν 14(B 2; 898.4 cm −1) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν 4 and ν 9 bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν 5 and ν 14 bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant ς 14 , 5 c . The ν 2 band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν 10 + ν 14 band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.

The high-resolution infrared spectrum of thiophene between 600 and 1200cm−1: A spectroscopic and theoretical study of the fundamental bands ν6, ν7, ν13, and the c-Coriolis interacting dyad ν5, ν19

Abstract The Fourier transform infrared spectrum of gaseous thiophene, C4H4S, has been recorded in the 600–1200 cm−1 spectral region with a resolution of ca. 0.0030 cm−1. Five fundamental bands ν13 (B1, 712.1 cm−1), ν7 (A1; 840.0 cm−1), ν6 (A1; 1036.4 cm−1), ν5 (A1; 1081.5 cm−1) and ν19 (B2; 1084.0 cm−1) have been analysed by the standard Watson model (A-reduction). Ground state rotational and quartic centrifugal distortion constants have been obtained from a simultaneous fit of ground state combination differences from four of these bands and previous microwave transitions. Upper state spectroscopic constants have been obtained for all five bands from single band fits using the Watson model. A strong c-Coriolis resonance perturbs the close lying ν5 and ν19 bands. We have analysed this dyad system by a model including first and second order Coriolis resonance using the theoretically predicted Coriolis coupling constant ς 19 , 5 c . From this analysis we locate the previously unobserved ν19 band at 1083.969 cm−1. The rotational constants, ground state quartic centrifugal distortion constants, anharmonic frequencies, and vibration–rotational constants (α-constants) predicted by quantum chemical calculations using a cc-pVTZ basis with B3LYP methodology, are compared with the present experimental data, where there is generally good agreement. A complete set of anharmonic frequencies and α-constants for all fundamental levels of the molecule is given.

The stretching fundamental bands ν1, ν2 and ν4 of H 28SiD 3

The ν 1(A 1), Si–H stretching, ν 2(A 1) and ν 4(E), Si–D stretchings, fundamental bands of HSiD 3 have been recorded at an effective resolution of ca. 0.003 cm −1 between 2080 and 2280 cm −1 and between 1480 and 1720 cm −1, respectively. Ro-vibrational transitions of the H 28SiD 3 isotopologue have been assigned in the two spectral ranges, about 700 belonging to ν 1, with J′ up to 25 and K up to 21, and about 1600 to the ν 2/ ν 4 dyad, with J′ up to 24 and K′ up to 19. The spectra of all the bands evidence the existence of several perturbations. The transitions of ν 1 have been analyzed either neglecting or including in the model A 1/E Coriolis-type interactions with nearby dark states. The υ 2 = 1 and υ 4 = 1 states have been fitted simultaneously taking into account several ro-vibrational interactions between them and, in addition, with the υ 5 = 2, l = 0 component, and with few other close dark states. The standard deviation of the fit for both ν 1 and the ν 2/ ν 4 dyad is, however, more than one order of magnitude larger than the estimated experimental precision and is independent on the adopted model.

Local mode and normal mode models for molecules with two non-equivalent C–H bonds

For molecules with C–H bonds, a local mode description of the bonds is often adopted to interpret the C–H stretching overtone spectra, although a representation in terms of normal modes is also possible. The equivalence between the two alternative representations demands simple numerical equations between the normal mode anharmonicity constants x rs and the quartic anharmonic coupling constants K rstu , the so-called ‘x–K relations’. The relations appropriate for low symmetry molecules with two non-equivalent C–H bonds (ν1, ν2), such as XHC = CHY, are derived in this paper. The consequences of these relations are illustrated with a detailed analysis of the C–H stretching overtone region, where the naive application of the relations obtained for more symmetric molecules could lead to a different interpretation of the overtones 2v 1 and 2ν2 and of the combination band ν1 + ν2. The relations are tested with theoretical calculations for difluoro- and chlorofluoro-substituted ethenes, propadiene, and butatrienes.

Substrate-specific Interactions with the Heme-bound Oxygen Molecule of Nitric-oxide Synthase

We report the characterization by resonance Raman spectroscopy of the oxygenated complex (Fe(II)O(2)) of nitric-oxide synthases of Staphylococcus aureus (saNOS) and Bacillus subtilis (bsNOS) saturated with N(omega)-hydroxy-l-arginine. The frequencies of the nu(Fe-O) and nu(O-O) modes were 530 and 1135 cm(-), respectively, in both the presence and absence of tetrahydrobiopterin. On the basis of a comparison of these frequencies with those of saNOS and bsNOS saturated with l-arginine (nu(Fe-O) at 517 cm(-1) and nu(O-O) at 1123 cm(-1)) and those of substrate-free saNOS (nu(Fe-O) at 517 and nu(O-O) at 1135 cm(-1)) (Chartier, F. J. M., Blais, S. P., and Couture, M. (2006) J. Biol. Chem. 281, 9953-9962), we propose two models that account for the frequency shift of nu(Fe-O) (but not nu(O-O)) upon N(omega)-hydroxy-l-arginine binding as well as the frequency shift of nu(O-O) (but not nu(Fe-O)) upon l-arginine binding. The implications of these substrate-specific interactions with respect to catalysis by NOSs are discussed.

Effect of high foreign-gas pressures on perpendicular and hybrid IR absorption bands for symmetric top molecules

The effect of high foreign-gas pressure (He, Ar, N2 up to 220 atm and CO2 up to 90 atm) on the contours of perpendicular and hybrid IR absorption bands for symmetric top molecules has been studied. It has been established that over the entire studied pressure range, the shape of the contours of the perpendicular vibrational bands ν4 and ν5 for chloroform, deuterochloroform, and bromoform is stable and changes relatively little as the pressure increases. The effect of collisions on the band contours is estimated by comparing the contours for mixtures of compressed gases with the contours calculated in the approximation of the J-and M-diffusion models. It has been shown that intramolecular perturbation of free rotation by Coriolis forces is the determining factor in formation of the contours of the perpendicular bands, successfully competing with the perturbing effect of the foreign gases, evidence for which comes from the insignificant changes in the shape of the bands as the pressure of the foreign gases increases.

High accurate peak positions for calibration purposes with the lowest fundamental bands ν2 of N 2O and CO 2

The lowest fundamental vibration rotation bands ν 2 of nitrous oxide (N 2O) and carbon dioxide (CO 2) have been measured with a Fourier transform spectrometer at the resolution of 0.001 cm −1. The spectra have been calibrated with the high accurate peak positions of the carbonyl sulfide (OCS) ν 2 band, which has been recently produced as a candidate for a secondary standard by calibrating first the 2 ν 2 band with the CO 2 laser bands around 10 μm and then transferring the calibration to ν 2 with the internal energy levels of OCS. In the present work the OCS ν 2 and ν 1 bands were measured together with the spectra of N 2O and CO 2. Then the OCS ν 1 band was measured by calibrating it with the 2 ν 2 band of OCS. The linearity of the wavenumber scale was checked by comparing the corresponding line positions in the OCS ν 1 band in these two separate measurements. The absolute accuracy of the ν 2 band centers of N 2O and CO 2 were evaluated to be 6.8 × 10 −6 and 8.4 × 10 −6 cm −1, respectively.

High resolution study of AsHD 2: Ground state and the three bending fundamental bands ν3, ν4, and ν6

For the first time the infrared spectrum of the AsHD 2 molecule has been measured in the region of the bending fundamental bands ν 3, ν 4, and ν 6 on a Fourier transform spectrometer with a resolution of 0.0024 cm −1 and analyzed. More than 5500 transitions with J max = 26 have been assigned and used both to obtain “ground state combination differences” and for the determination of upper state ro-vibrational energies of the triad (001000), (000100), and (000001). Rotational parameters including centrifugal distortion coefficients up to octic terms of the ground vibrational state were calculated by fitting more than 500 “ground state combination differences” with J max and K a max = 21 . The obtained set of 24 parameters provides a rms-deviation of 0.00011 cm −1. The upper energies were fitted with 52 parameters of an effective Hamiltonian which takes into account strong resonance interactions between all vibrational states of the triad (001000), (000100), and (000001). The rms-deviation for the energy levels considered in the fit is 0.00014 cm −1.

The high resolution infrared bands ν1, ν2, ν4 and ν2 + ν5 of F 37Cl 16O 3

The high resolution infrared spectrum of mono-isotopic F 37Cl 16O 3 has been studied in the regions of ν 1, ν 2, ν 4 and ν 2 + ν 5 bands, centered at 1060.20, 707.16, 1301.71 and 1292.15 cm −1, respectively. The ν 1 and ν 2 parallel bands are unperturbed so their analysis was straightforward and 3355 and 2433 transitions were assigned, respectively. The band origins, the rotational and centrifugal molecular constants in the v 1 = 1 and v 2 = 1 states have been determined, with standard deviation of the fits σ = 0.00019 and 0.00018 cm −1. The ν 4 fundamental is affected by an anharmonic resonance with the ν 2 + ν 5 combination band. The kl > 0 sublevels cross at kl ⩾ 27 because of the opposite values of A ζ 4 z and A ζ 25 z . The anharmonic resonance constant W 245 F = 2.7991246 ( 358 ) cm −1 has been derived. The Δ l = Δ k = ±2 and Δ l = 0, Δ k = ±3 essential resonances have been found to be effective in ν 4, while in ν 2 + ν 5 only the Δ l = Δ k = ±2 one was active. A total of 5721 transitions have been assigned, 25% of them belonging to ν 2 + ν 5. The rovibrational parameters and the interaction constants of F 37Cl 16O 3 have been obtained. The standard deviation of the fit is 0.0006 cm −1, six times the estimated data precision. The equilibrium geometry of perchloryl fluoride has been determined from the A e and B e constants of F 35Cl 16O 3 and F 37Cl 16O 3. Using the A 0 and B 0 constants of all the symmetric species the r 0 geometry has also been derived.

X-ray and IR analysis of Cu-Si ferrite

Abstract Polycrystalline soft ferrite, Cu1+xSixFe2−2xO4 ( x = 0.0 , 0.05, 0.1, 0.15, 0.2 and 0.3) were prepared by standard ceramic technique. The X-ray analysis confirmed the single phase formation of the samples up to x = 0.1 beside a second phase for x⩾0.15. The lattice parameter was found to decrease with composition(x), which is attributed to ionic size difference of cations involved. The bulk density measurements shows two different behavior for x 0.15. The IR spectra of Cu–Si ferrite system have been analyzed in the frequency range 200–1200 cm−1. It revealed two prominent bands ν1 and ν2 which are assigned to tetrahedral and octahedral metal complexes, respectively. The position of the highest frequency band is around 575 cm−1 while the lower frequency band is around 400 cm−1.

High resolution FTIR spectroscopy on CH2DI and CHD2I: analyses of the fundamental bands ν6' and ν6''

The H–C–I and D–C–I deformations, i.e. ν6' and ν6″ fundamental vibration bands of the methyl iodide molecules CH2DI and CHD2I have been investigated with high resolution (0.001 cm−1) Fourier transform infrared spectra in the region 600–1000 cm−1 for CH2DI and 550–850 cm−1 for CHD2I. For CH2DI ν6′ appears as a hybrid a/b-type band and ν6″ as a c-type band. For CHD2I the corresponding types are hybrid a/c and b. We have been able to assign more than 12 000 transitions in the case of CH2DI and over 11 000 transitions in the case of CHD2I. The upper and ground state parameters have been obtained by fitting these transitions to the A reduced Watson's Hamiltonian. The interactions between the states v6′=1 and v6″=1 have also been investigated.

Analytical representation for water vapor self-broadening coefficients

Analytical models are proposed for the water vapor self-broadening coefficients γ, which depend on the fitting parameters and the temperature. The model parameters are determined for the rotational transitions of the ground vibrational state and the band ν2. The calculated values of γ are compared systematically with the experimental findings and with the results of calculation by semiclassical methods. The models proposed reconstruct quite satisfactorily the experimental values of γ known for different temperatures and can be used to tabulate γ for the bands under study in a wide range of temperatures and rotational quantum numbers.

The Totally Symmetric Vibrations of NH3···HF and NH3···HCN: a CCSD(T) Study Including Anharmonicity Effects

Abstract The coupled cluster variant CCSD(T) has been employed to calculate potential energy and dipole moment surfaces for the hydrogen-bonded complexes NH3···HF and NH3···HCN, restricting the treatment to the totally symmetric coordinates. Both complexes have C 3ν symmetry, with equilibrium dissociation energies (D e) predicted to be 52.1 and 27.1 kJ mol−1, respectively. Vibrational term energies and wavefunctions as well as absolute IR intensities are calculated under inclusion of anharmonicity effects. In contrast to previous theoretical work for NH3···HF, the umbrella bending vibration of this complex as well as for NH3···HCN is found to be rather anharmonic. The familiar double harmonic approximation fails to yield reliable values for the IR intensities of the NH3 (ND3) symmetric stretching vibrations of either NH3···HF or ND3···DF. The wavenumbers of the intermolecular stretching vibrations are predicted as ν4 = 277 cm−1 (NH3···HF) and ν5 = 154 cm−1 (NH3···HCN). Owing to a large quadratic coupling term in the electric dipole moment function, the band ν4(NH3···HF) has virtually zero intensity. The effects of deuterium substitution on wavenumbers and IR intensities have been studied for both complexes.

Interferometric determination of the dispersion of the vibrational polarizability and the integral intensities of fundamental bands of trifluorochloromethane molecules CF3Cl

Using two-color interferometry, the dispersion of the refraction and the vibrational polarizability of freon molecules CF3Cl of natural isotopic composition was studied in the lasing range of an IR laser on the basis of the main isotopomer of carbon dioxide (12C16O2). Simultaneous processing of the data of the absolute refractometric and relative absorption measurements using the Kramers-Kronig formalism made it possible to refine the integral intensities of the fundamental vibrational bands ν1 and ν4 and to determine the dispersion of the vibrational polarizability in the range from 1050 to 1250 cm−1.

Integral intensities of absorption bands of silicon tetrafluoride in the gas phase and cryogenic solutions: Experiment and calculation

The spectral characteristics of the SiF4 molecule in the range 3100–700 cm−1, including the absorption range of the band ν3, are studied in the gas phase at P = 0.4–7 bar and in solutions in liquefied Ar and Kr. In the cryogenic solutions, the relative intensities of the vibrational bands, including the bands of the isotopically substituted molecules, are determined. The absorption coefficients of the combination bands 2ν3, ν3 + ν1, ν3 + ν4, and 3ν4 are measured in the solution in Kr. In the gas phase of the one-component system at an elevated pressure of SiF4, the integrated absorption coefficient of the absorption band ν3 of the 28SiF4 molecule was measured to be A(ν3) = 700 ± 30 km/mol. Within the limits of experimental error, this absorption coefficient is consistent with estimates obtained from independent measurements and virtually coincides with the coefficient A(ν3) = 691 km/mol calculated in this study by the quantum-chemical method MP2(full) with the basis set cc-pVQZ.

Analysis of the Fourier transform infrared spectrum of�the�stannane species 116SnH4 in the region 1270?1600�cm-1

Monoisotopic stannane 116SnH4 has been investigated at room temperature in the 600–850 cm-1 and 1270–1600 cm-1 regions by FTIR spectroscopy with an effective resolution of 2.1 ×10-3 cm-1 and 2.0 ×10-3 cm-1 respectively. The simultaneous analysis of infrared transitions of both the bending triad and the hot band {bending triad} minus {bending dyad}, enabled us to determine 26 parameters for the (2ν2) band and the combination band (ν2+ν4). The standard deviation of the fit was about 1.5×10-3 cm-1. In this analysis, we have used, for the bending triad, a Hamiltonian developed to the fourth order of approximation. 163 observed transitions for the hot band and most observed transitions for the bending triad spectrum, were assigned to the two bands 2ν2 and (ν2+ν4), up to J=9. In the fit of the Hamiltonian parameters, we have used for the ground state and for the fundamentals ν2 and ν4, the parameters determined by Brunet, Pierre, and Burger [J. Mol. Spectrosc. 140, 237 (1990)].

High resolution Fourier transform infrared spectroscopy on CH2DI and CHD2I: evaluation of the ground state constants and analyses of the C-I stretching bands ν3

Abstract The high resolution (0.0010cm−1) Fourier transform infrared spectra of the partially deuterated methyl iodide molecules CH2DI and CHD21 have been recorded and analysed in the ν3 band regions around 510cm−1. The fundamental band ν3 is associated with the stretching of the C-I bond and the spectra appear therefore as an asymmetric rotor hybrid a/b-type band and hybrid a/c-type band for CH2DI and CHD2I, respectively. About 4700 transitions in the case of CH2DI and about 3900 transitions in the case of CHD2I have been assigned. The ground state rotational constants of CH2DI and CHD2I have been obtained using the ground state combination differences calculated from the assigned ν3 transitions and 16 microwave transitions from literature. The S reduced Watson's Hamiltonian has been used in the calculations. In addition, the upper state parameters describing the v3=1 vibrational states of these molecules have been determined. The obtained ground state constants as well as the upper state parameters have been compared to the corresponding constants of the symmetric top species CH3I and CD3I