共查询到20条相似文献,搜索用时 15 毫秒
1.
Geoffrey DuxburyAlexander Alijah 《Journal of Molecular Spectroscopy》2002,211(1):31-57
The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the rovibronic energies in the region where the vibronic states of the excited Ã2A1 electronic state of NH2 interact with near-resonant high-lying levels of the X?2B1 state of NH2. A detailed comparison has been made with the experimental measurements which were made of these rovibronic states, the majority of which are due to Ramsay, Vervloet, and their collaborators. We have shown that, as in our study of the vibronic levels of the X?2B1 state below the barrier to linearity, in order to fit the variation of the effective vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, ASO must be increased from the earlier value of 50 cm−1 of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm−1. The impact of Fermi resonance, in both the Ã2A1 and X?2B1 states, on the observed rovibronic structure has been assessed. The pattern of calculated spin-rovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally. 相似文献
2.
The stretch-bender model, developed originally to describe the effects of stretch-bend interactions and Renner-Teller coupling in symmetrical triatomic molecules, has been extended to incorporate the effects of spin-orbit interaction and of overall rotation. A comparison is made between the treatment of spin-orbit interaction and of overall rotation in our model and in the MORBID approach of P. Jensen, M. Brumm, W. P. Kraemer, and P. R. Bunker (J. Mol. Spectrosc.171, 31-57 (1995)). 相似文献
3.
Haruki IshikawaYasuhiko Muramoto Naohiko Mikami 《Journal of Molecular Spectroscopy》2002,216(1):90-97
Stimulated emission pumping spectra of the Ã1B1-X?1A1 transition of the SiH2 radical were observed in order to obtain information about the ã3B1 state through the spin-orbit interaction. The vibrational level structure of the X? state, which is the basis for the present observation of the triplet state, was well described with a polyad structure, in which both the 1ν1 : 2ν2 Fermi and the 2ν1 : 2ν3 Darling-Dennison anharmonic resonances were considered. In the P=10 polyad, four sets of spin-orbit perturbations were observed for the first time. The triplet state observed at about 9640 cm−1 from the (000) level of the X? state was tentatively assigned as the ã3B1 (030) level. An analysis of the spin-orbit interaction showed that the interaction energies of the spin-orbit coupling are 0.73-3.13 cm−1. This value is rather smaller than that expected based on the comparison with CH2. This is considered to be due to poor overlap between the vibrational wave functions in the ã and the X? state. 相似文献
4.
Tsuneo HiranoKeisaku Ishii Tina Erica Odaka Per Jensen 《Journal of Molecular Spectroscopy》2002,215(1):42-57
The MgNC radical was the first Mg-containing species to be observed in interstellar space. This fact has stimulated considerable spectroscopic interest in this molecule, and in its isomer MgCN, but nevertheless the only rotationally resolved spectroscopic data presently available for X?2Σ+ MgNC comprise the rotational spectrum (K. Kawaguchi et al., 1993, Astrophys. J.406, L39-L42; K. Ishii et al., 1993, Astrophys. J.410, L43-L44; M. A. Anderson and L. M. Ziurys, 1994, Chem. Phys. Lett.231, 164-170; E. Kagi et al., 1996, J. Chem. Phys.104, 1263-1267; E. Kagi and K. Kawaguchi, J. Mol. Spectrosc. 2000, 199, 309-310) together with a few vibronic bands, all originating in the vibronic ground state and belonging to the Ã2Π←X?2Σ+ electronic transition (R. R. Wright and T. A. Miller, 1999, J. Mol. Spectrosc.194, 219-228). For MgCN, only the rotational spectrum in the vibrational ground state is known (M. A. Anderson, T. C. Steimle, and L. M. Ziurys, 1994, Astrophys. J.429, L41-L44). We report here potential energy surfaces calculated by the Averaged Coupled-Pair Functional (ACPF) method with TZ3P+f (Mg), TZ2P+f(N,C) basis sets including core-valence correlation due to the Mg 2s and 2p electrons. The ab initio results are used for determining the standard spectroscopic constants of X?2Σ+ MgNC and MgCN. Also, we report variational calculations of the rotation-vibration energies, and variational simulations of the lowest rotation-vibration bands, carried out with the MORBID program system (P. Jensen, 1988, J. Mol. Spectrosc.128, 478-501). We hope that our theoretical results will encourage and facilitate further characterization of X?2Σ+ MgNC and MgCN by high-resolution spectroscopy. 相似文献
5.
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
6.
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
7.
8.
Timothy C. Steimle Robert R. BousquetKei-ichi C. Namiki Anthony J. Merer 《Journal of Molecular Spectroscopy》2002,215(1):10-28
The 000-000 and 310 bands of the 775-nm electronic transition of YC2(Ã2A1←X?2A1) have been studied at high resolution, using the laser-induced fluorescence from a supersonic jet expansion. Three types of experiment have been carried out. First, the complete rotational and hyperfine structures of the two bands were recorded. To measure the small asymmetry splittings in the K=2 levels of the X?2A1 state, portions of the b-type 310 band were then recorded in the presence of a weak static electric field. Finally, a number of pure rotational transitions between the K=0 levels of the ground state were recorded by pump/probe microwave optical double resonance. A few small rotational perturbations occur in the upper electronic state but, omitting the perturbed lines, the combined data sets could be modeled using an effective Hamiltonian operator appropriate for the rotation, electron spin, and hyperfine structure of a rigid asymmetric top molecule. The molecule is confirmed as being “T-shaped,” where the Y atom is bonded to the side of a C2 group; the rotational constants determined are for the Ã2A1, 31 level, A=1.76128, B=0.189949, C=0.170056 cm−1, and for the X?2A1, v=0 level, A=1.742731, B=0.201947, C=0.181285 cm−1. Allowing for electron orbital corrections to the rotational constants, the geometrical structures are found to be Ã2A1 state, r (Y-C)=2.2795 Å, r (C-C)=1.2630 Å, ∠C-Y-C=32.17°; X?2A1 state, r (Y-C)=2.1946 Å, r (C-C)=1.2697 Å, ∠C-Y-C=33.63°. A molecular orbital diagram is given for the states of YC2 and the interpretation of the electron spin and hyperfine parameters is discussed. 相似文献
9.
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
10.
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
11.
The second overtone band 3ν1 of sulfur dioxide has been studied for the first time with high resolution rotation-vibration spectroscopy. About 3000 transitions involving about 900 upper state energy levels with have been assigned to the 3ν1 band. In the analysis, an effective Hamiltonian taking into account accidental interactions between the vibrational states (3 0 0), (2 2 0), and (0 4 1) was used. The Watson operator in A-reduction and Ir representation was used in the diagonal blocks of the Hamiltonian. As the result of analysis a set of parameters reproducing the initial experimental data with the rms = 0.00028 cm−1 was obtained. 相似文献
12.
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
13.
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
14.
The ν1 fundamental band of the ClO2 radical has been studied by means of the 10.6-μm CO2 and N2O laser Stark spectroscopy. More than 250 and 150 Stark resonances were assigned for the 35ClO2 and 37ClO2 species, respectively, and were analyzed together with the recent microwave and laser-microwave double resonance results to give molecular constants including spin-rotation interaction constants. The ν1 band origins and electric dipole moments both in the ground and ν1 states were determined accurately
35ClO2 | 37ClO2 | |||||
945.592 357(60) | 939.602 909(66) | cm?1 | ||||
μ′ | 1.788 39(13) | 1.788 46(15) | D | |||
μ″ | 1.791 95(10) | 1.792 10(13) | D | |||
δμ | ?0.003 56(18) | ?0.003 64(26) | D |