Laboratory Measurements of the Hyperfine Structure of H 14 N 12 C and D 14 N 12 C (original) (raw)
Related papers
Physical Chemistry Chemical Physics, 10, 5599 (2008)
Large-amplitude molecular motions which occur during isomerization can cause significant changes in electronic structure. These variations in electronic properties can be used to identify vibrationally-excited eigenstates which are localized along the potential energy surface. This work demonstrates that nuclear quadrupole hyperfine interactions can be used as a diagnostic marker of progress along the isomerization path in both the HC 14 N/H 14 NC and DC 15 N/D 15 NC chemical systems. Ab initio calculations at the CCSD(T)/cc-pCVQZ level indicate that the hyperfine interaction is extremely sensitive to the chemical bonding of the quadrupolar 14 N nucleus and can therefore be used to determine in which potential well the vibrational wavefunction is localized. A natural bonding orbital analysis along the isomerization path further demonstrates that hyperfine interactions arise from the asphericity of the electron density at the quadrupolar nucleus. Using the CCSD(T) potential surface, the quadrupole coupling constants of highly-excited vibrational states are computed from a one-dimensional internal coordinate path Hamiltonian. The excellent agreement between ab initio calculations and recent measurements demonstrates that nuclear quadrupole hyperfine structure can be used as a diagnostic tool for characterizing localized HCN and HNC vibrational states.
Angewandte Chemie International Edition, 47, 2969 (2008)
The making and breaking of bonds in chemical reactions necessarily involve changes in electronic structure. Therefore, measurements of a carefully chosen electronic property can serve as a marker of progress along a reaction coordinate and provide detailed mechanistic information about the reaction. Herein, we demonstrate through high-resolution spectroscopic measurements and high-level ab initio calculations that nuclear quadrupole hyperfine structure (hfs), an indicator of electronic structure, is highly sensitive to the extent of bending excitation in the prototypical HCNQHNC isomerization system. Thus, measurements of hfs show how the nature of a chemical bond is altered when a vibration that is coupled to the isomerization reaction coordinate is excited.
Rotational spectrum of and : completely resolved nuclear hyperfine structures due to and
Journal of Molecular Spectroscopy, 2003
The pure rotational spectrum of 13 C 17 O has been observed in the millimeter-and submillimeter-wave region using the Lamb-dip technique in order to increase the instrumental resolving power and so to resolve both the hyperfine structure due to 17 O and that due to 13 C. In this way very accurate values of the rotational and centrifugal distortion constants, the 17 O nuclear electric quadrupole coupling constant and the 17 O and 13 C spin-rotation constants have been obtained. In addition, the J ¼ 1 0 and J ¼ 2 1 transitions of 13 C 18 O have been recorded using the Lamb-dip technique. The resolved hyperfine structure of these transitions allowed us to determine the rotational and 13 C spin-rotation constants. The experimental determination of all these parameters has been supported by ab initio computations.
Infrared Transitions of H12C14N and H12C15N between 500 and 10000 cm−1
Journal of Molecular Spectroscopy, 1996
We have measured the Fourier transform spectrum ( FTS ) of two isotopomers of hydrogen cyanide ( H 12 C 14 N and H 12 C 15 N ) from 500 to 10 000 cm 01 . The infrared data have been combined with earlier published microwave and submillimeter-wave measurements. From this analysis new vibration -rotation energy levels and constants are given, based on the observation of a number of new vibrational levels, especially for H 12 C 15 N. The Coriolis interaction involving D£ 3 Å 01, D£ 2 Å 3, and Dl Å {1 has been observed for a great many levels and in some cases the assignments of laser transitions allowed by this interaction are more clearly shown. New vibrationrotation constants are given that allow one to predict the transition wavenumbers for most of the transitions below 10 000 cm 01 with accuracies of about 0.5 cm 01 or better. Values are given for the power series expansion of the l -type resonance constants and for the centrifugal distortion constants, as well as the usual vibrational and rotational constants. ᭧
Re-examination of the hyperfine structure of 14NH2
The Journal of Chemical Physics, 1995
The hyperfine structure of the 14 NH 2 radical is investigated by means of multireference single and double configuration interaction ͑MRCI͒ techniques. Particular attention is paid to the dependence of the coupling constants on the basis set, reference space, and configuration selection energy threshold. It is found that convergence can be obtained only if more than 83 reference configurations are included with an energy threshold of at least 10 Ϫ7 hartree. With up to 126 reference configurations, an energy threshold smaller than 10 Ϫ8 hartree and an uncontracted ͑13s8p2d/8s2p͒ basis set, the MRCI isotropic couplings ͑27.44 and Ϫ68.47 MHz for N and H, respectively͒ are in very good agreement with experimental data ͑27.9 and Ϫ67.2 MHz, respectively͒.
Theoretical calculations of the nuclear quadrupole coupling in the spectra of D3+, H2D+, and HD2+
Journal of Molecular Spectroscopy, 1991
The present paper reports a purely theoretical calculation ofthe quadrupole hyperfine structure in the rotation-vibration spectra of D;, HlD', and HD; As the initial step in the calculation we have computed ab initio extensive sets of electric tield gradient values for these molecules. These ab initio values are used. together with rotation-vibration wavefunctions obtained using the rotation-vibration theory developed previously for X, and Y,X equilateral triangular molecules [V. Spirko, P. Jensen, P. R. Bunker, and A. Cejchan, J. Mol. Spectrosc. 112, 183-202 (1985); P. Jensen, V. Spirko, and P. R. Bunker, J. Mol. Spectrosc. 115, 269-293 ( 1986)] to obtain the quadrupole splitting parameters for the individual rotation-vibration states of the molecules in question. We have calculated actual quadrupole splittings for selected transitions of H2D+ and HD; and find these to be less than 100 kHz. Laboratory measurements of these small splittings would require sub-Doppler resolution and do not seem feasible at the present time. Even in cold interstellar clouds HtD+ lines certainly have widths larger than the calculated splittings so that interstellar detection of the splittings is impossible. Clearly in the present study theory is very far ahead of experiment. One might hope that in a not-too-distant future experimental techniques will be developed which allow the observation of the small splittings. cc')
Journal of Molecular Structure, 2002
The nuclear quadrupole coupling hyper®ne structure arising in the rotational spectra of dichloro¯uoromethane and pyridazine due to the presence of two equivalent quadrupolar nuclei (Cl and N, respectively) has been investigated using molecular beam Fourier transform microwave spectroscopy in the 6±18 GHz frequency range. For dichloro¯uoromethane the species CH 35 Cl 2 F, CH 35 Cl 37 ClF and CH 37 Cl 2 F have been investigated whereas for pyridazine only the parent species with two 14 N has been observed. Thanks to the sub-Doppler resolution and high sensitivity inherent to this technique, the hyper®ne structure for the low J transitions has been resolved and the complete nuclear quadrupole coupling tensors have been determined. Diagonalization of the tensor for dichloro¯uoromethane molecule has given interesting information which reveals very small deviations between the Cl nuclei quadrupole coupling tensors principal axes z and the ClC bonds. The experimental results have been compared with those from MP4/6-3111G(2d,2p) ab initio calculations. q
Laser-Rf double-resonance studies of the hyperfine structure of metastable atomic states of55Mn
Zeitschrift für Physik A: Atoms and Nuclei, 1979
The hyperfine structure (hfs) of the metastable atomic states 3d64s 6D1/2,3/2, 52, 7/2,9/2 of 55Mn was measured using the ABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence). The hfs constants A and B, corrected for second order hfs perturbations, could be derived from these measurements. The theoretical interpretation of these corrected A-and B-factors was performed in the intermediate coupling scheme taking into account the configurations 3d54s 2, 3d64s and 3d 7. Examining the influence of the composition of the eigenvectors on the hfs parameters (r-'~)k~ k~ it was found, that for the configuration 3d64s the two-body magnetic interaction should be considered in the calculation of the eigenvectors. Investigating second order electrostatic configuration interactions and relativistic effects and using calculated relativistic correction factors we obtained for the nuclear quadrupole moment of the nucleus 55Mn a value of Q=0.33(1) barn, which is not perturbed by a shielding or antishielding Sternheimer factor. The following hfs constants have been obtained: A(1/2) = 882.056 (12) MHz A(3/2)=469.391 (7) MHz A(5/2)=436.715 (3) MHz A(7/2)= 458.930 (3) MHz A(9/2)= 510.308 (8) MHz B(3/2) =-65.091 (50) MHz B(5/2) =-46.769(30) MHz B(7/2)= 21.701(40) MHz B(9/2)= 132.200(120) MHz
Submillimeter spectrum and analysis of vibrational and hyperfine coupling effects in (HI)2
Chemical Physics Letters, 2009
Observed rotational-vibrational transitions of HI dimer in the geared bending mode, centered at 511.9 GHz, are reported. This $50 kHz spectrum was recorded using a co-axially configured pulsed jet submillimeter spectrometer and hyperfine structure of R(J) and P(J) transitions from the quadrupole moments of iodine nuclei are completely resolved for low-J transitions. Analysis of hyperfine patterns was carried out using a theoretical approach accounting for the large amplitude motion effects and hyperfine matrix elements within and between vibrational states. The submillimeter analysis is consistent with a vibrationally averaged ground state R cm = 4.56372(1) Å and average bending angle h = 46.405(1)°.