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1.
The infrared spectra of the 2ν1, 2ν2 and 2ν3 overtones of perchloryl fluoride, FClO3, have been recorded at high resolution using monoisotopic pure samples. Four symmetric top species have been investigated: F35Cl16O3, F37Cl16O3, F35Cl18O3 and F37Cl18O3. The vi = 2, i = 1, 2, 3 vibrationally excited states are totally symmetric, so these overtones correspond to parallel bands of medium/weak intensity, centered from 2010 to 2120 cm−1 (2ν1), from 1390 to 1430 cm−1 (2ν2) and from 1070 to 1100 cm−1 (2ν3). Most of the bands are unperturbed and their analysis was straightforward. The band origins, the rotational and centrifugal molecular constants in the v1 = 2, v2 = 2 and v3 = 2 states have been determined, with standard deviations of the fits from 0.00024 to 0.00067 cm−1. The 2ν1 overtones of F35Cl16O3 and F37Cl16O3 are perturbed by an A1/E Coriolis resonance between the v1 = 2 state and one E component of the v4 = 1, v6 = 2 manifold. The 2ν2 of F37Cl18O3 is perturbed by the same kind of interaction involving the v1 = v6 = 1 (E) state, at about 1396 cm−1. In these bands the resonance is localized on rotational levels with specific J and K values. As a consequence, a few transitions of the perpendicular bands involving the interacting levels could be identified in the spectra. A simultaneous fit of the transitions assigned to the dyads has been performed and the parameters of the excited states have been determined, including the high order Coriolis interaction coefficient . The anharmonic constants x11, x22, x33 of all the studied isotopologues of FClO3, x46 of F35Cl16O3, x46 + g46 of F37Cl16O3 and x16 of F37Cl18O3, have been derived. 相似文献
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3.
O.N. Ulenikov E.S. Bekhtereva O.L. Petrunina H. Bürger 《Journal of Molecular Spectroscopy》2003,219(1):13-29
The P-H stretching bands ν1/ν5 and 2ν1/ν1+ν5 were recorded using a Bruker 120 HR interferometer with a resolution of 0.0042 and 0.0088 cm−1, respectively, and analyzed. From the fits 33 and 50, respectively, vibrational, rotational, centrifugal distortion, and resonance interaction parameters were obtained. These reproduce 668 and 497 rovibrational energies of the pairs of states ν1/ν5 and 2ν1/ν1+ν5 with experimental accuracies, rms=0.00016 and , respectively. “Local mode” behavior of the PH2 fragment is established and discussed in detail. 相似文献
4.
Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH3 perturbed by O2 at room temperature (T = 295 K) in some branches of the ν2, 2ν2, and ν4 bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm−1. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O2 pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν4 band. They are positive for the ν2 and 2ν2 bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential. 相似文献
5.
C Betrencourt-Stirnemann G Graner D.E Jennings W.E Blass 《Journal of Molecular Spectroscopy》1978,69(2):179-198
Previous studies of the parallel bands 2ν2 and of CH3Br by the two first authors have been completed by the analysis of the weaker perpendicular band ν2 + ν5, centered near 2745 cm?1. It is well known that the v2 = 1 and v5 = 1 states of methylbromide are linked by an x-y-type Coriolis interaction. Therefore, in the 2500–2900-cm?1 range, the levels are linked by a similar interaction. Least-squares and prediction programs have been written to treat this kind of problems and they have been satisfactorily applied to both isotopic species, CH379Br and CH381Br. A localized resonance in the K = 0 subband of ν2 + ν5 has been shown to be due to the 3ν3 + ν6 band. No evidence for a strong Fermi resonance between ν1 and has been found. 相似文献
6.
The high resolution infrared spectrum of mono-isotopic F37Cl16O3 has been studied in the regions of ν1, ν2, ν4 and ν2 + ν5 bands, centered at 1060.20, 707.16, 1301.71 and 1292.15 cm−1, respectively. The ν1 and ν2 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 v1 = 1 and v2 = 1 states have been determined, with standard deviation of the fits σ = 0.00019 and 0.00018 cm−1. The ν4 fundamental is affected by an anharmonic resonance with the ν2 + ν5 combination band. The kl > 0 sublevels cross at kl ? 27 because of the opposite values of and . The anharmonic resonance constant cm−1 has been derived. The Δl = Δk = ±2 and Δl = 0, Δk = ±3 essential resonances have been found to be effective in ν4, while in ν2 + ν5 only the Δl = Δk = ±2 one was active. A total of 5721 transitions have been assigned, 25% of them belonging to ν2 + ν5. The rovibrational parameters and the interaction constants of F37Cl16O3 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 Ae and Be constants of F35Cl16O3 and F37Cl16O3. Using the A0 and B0 constants of all the symmetric species the r0 geometry has also been derived. 相似文献
7.
We report the first high resolution rovibrational analysis of the infrared spectrum of pyrimidine (C4H4N2) based on measurements using our Fourier transform spectrometer, the Bruker IFS 125 HR Zürich Prototype (ZP) 2001. Measurements were conducted at room temperature in a White-type cell with effective optical path lengths between 3.2 and 9.6 m and with resolutions ranging from 0.0008 to 0.0018 cm−1 in the region between 600 and 1000 cm−1. The spectrum was analyzed in the ν4 (), ν10b () and ν6b regions of pyrimidine () using an effective Hamiltonian. A total of about 15 000 rovibrational transitions were assigned. The root mean square deviations of the fitted data are in the ranges drms = 0.00018-0.00024 cm−1, indicating an excellent agreement of experimental line data with the calculations. The results are discussed briefly in relation to possible extensions to spectra of DNA bases and to intramolecular vibrational redistribution at higher energy. The analysis of the ν10b and ν4 bands will also be useful in the interstellar search for pyrimidine in the infrared region. 相似文献
8.
Jean-Pierre Bouanich Jamel Salem Jacques Walrand 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(2):195-205
H2-broadening coefficients are measured for 41 transitions of PH3 in the QR branch of the ν2 band and the PP, RP, and PQ branches of the ν4 band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 2 to 16 and K from 0 to 11 are located between 995 and . 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 model provides larger broadening coefficients than the Voigt model. These coefficients γ0(J,K) are found to decrease slightly on the whole as J increases and they decrease significantly for K values approaching or equal to J(J?4). The H2-broadenings are also calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. The theoretical results are in satisfactory agreement with the experimental data and reproduce the J and K dependencies of the broadenings, but the decrease observed for the QR(J,K) transitions with K=J is notably overestimated. 相似文献
9.
Robert A. Toth 《Journal of Molecular Spectroscopy》2011,265(2):59-68
The necessity to revisit water spectroscopy at 6 μm was prompted by recent work indicating that some prior measurements of H216O line strengths (ranging through seven orders of magnitude) had larger than expected systematic errors for the stronger transitions. To investigate this, linestrengths of stronger transitions were re-measured (with 14 new H2O spectra recorded with a Bruker 125 HR Fourier transform spectrometer at the Jet Propulsion Laboratory) and combined with re-analyzed prior results (obtained at higher optical densities from 32 spectra recorded with the FTS at Kitt Peak). Systematic differences for some of the older data sets were identified and corrected. In this paper, an internally-consistent sampling of 1243 selected line strengths are reported for (0 1 0)-(0 0 0) and (0 2 0)-(0 1 0) transitions between 783 and 2378 cm−1. To confirm experimental precisions, observed and calculated line strengths are compared. 相似文献
10.
O.N. Ulenikov O.L. Khabibulina E.S. Bekhtereva H. Bürger 《Journal of Molecular Spectroscopy》2003,217(2):288-297
The infrared spectral regions of the P-D stretching fundamental band ν2 and the first overtone band 2ν2 of PH2D were recorded with a resolution of 2.7×10−3 and , respectively. In the analysis about 710 and 440 transitions were assigned to the ν2 and 2ν2 bands. These provided 358 and 268 upper rovibrational energy terms, respectively. Resonance interactions between the states (010000) and (000200) were taken into account in the Hamiltonian used to fit upper energies of the (010000) state. The rovibrational energies of the (020000) state were fitted with a Hamiltonian for an isolated vibrational state. 相似文献
11.
The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C2H2N2S, has been recorded with a resolution of ca. 0.003 cm−1 in the 800-1500 cm−1 spectral region. Five fundamental bands ν2(A1; 1391.9 cm−1), ν4(A1; 964.4 cm−1), ν5(A1; 894.6 cm−1), ν9(B1; 821.5 cm−1), and ν14(B2; 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 ν4 and ν9 bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν5 and ν14 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 . The ν2 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 ν10 + ν14 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. 相似文献
12.
The spectrum of the ν7 band of cis-ethylene-d2 (cis-C2H2D2) has been recorded with an unapodized resolution of 0.0063 cm−1 in the 740-950 cm−1 region using a Bruker IFS 125 HR Fourier transform infrared spectrometer. By fitting 2186 infrared transitions of ν7 with a standard deviation of 0.00060 cm−1 using a Watson’s A-reduced Hamiltonian in the Ir representation, accurate rovibrational constants for ν7 = 1 state have been derived. The band center of ν7 has been found to be 842.20957 ± 0.00004 cm−1. In a simultaneous fit of 1331 infrared ground state combination differences from the present ν7 transitions, together with 22 microwave frequencies, ground state constants have been improved. The rms deviation of the ground state fit was 0.00027 cm−1. 相似文献
13.
Jesus Lozano Ehsan Saadat Xiaojuan Li Sharmila Majumdar C. Benjamin Ma 《Magnetic resonance imaging》2009
Objective
The objective of this study was to develop quantitative T1ρ-weighted magnetic resonance imaging methodology for the detection and characterization of cartilage degeneration in a rabbit anterior cruciate ligament (ACL) transection model.Methods
The right knee ACLs of 18 adult female New Zealand white rabbits were transected. The left knee joint served as a sham control. The rabbits were euthanized at 3 (Group 1), 6 (Group 2) and 12 (Group 3) weeks postoperatively. High-resolution 3D fat-saturated spoiled gradient echo images and T1ρ-weighted images were obtained in both the sagittal and axial planes at 3 T using a quadrature wrist coil. Following MR analysis, histological slides from the lateral femoral condyle cartilage were graded using the Mankin grading system.Results
For all three groups, the average overall T1ρ values were significantly higher in the ACL-transected knee compared to control knee, and the percentage differences in T1ρ values between ACL-transected and control increased with the duration of time after transection. The average Mankin score for ACL-transected knees was higher than that for control for each time point, but this difference was statistically significant only for all groups combined.Conclusions
This study demonstrates the feasibility of using T1ρ-weighted imaging as a useful tool in the detection and quantification of cartilage damage in all knee compartments in an ACL-transected rabbit model of cartilage degeneration. 相似文献14.
The ν2 (CD3 symmetrical deformation) and ν5 (CD3 degenerate deformation) fundamental bands of CD3Br were studied by 9.4- and 10.4-μm CO2 laser Stark spectroscopy. Stark resonances originating from 28 and 53 rovibrational transitions of the ν2 and ν5 bands, respectively, were assigned for each of the isotopic species, CD379Br and CD381Br. These two bands were simultaneously analyzed with explicit inclusion of the ν2-ν5 Coriolis interaction, yielding precise molecular constants in the ν2 and ν5 excited states as well as the Coriolis coupling constant. The molecular constants obtained are consistent between the two isotopic species and are in good agreement with the results of high-resolution infrared studies. The band origins and dipole moments are
CD379Br | CD381Br | |||||
991.396 82 (18) | 991.388 46 (17) | cm?1 | ||||
1055.469 00 (12) | 1055.466 32 (12) | cm?1 | ||||
1.830 42 (52) | 1.829 84 (47) | D | ||||
1.829 93 (48) | 1.829 57 (46) | D | ||||
1.832 23 (60) | 1.831 19 (56) | D |