Cотрудники института
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Cотрудники института |
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Зобов Николай Федорович Область научных интересов: Профессиональная карьера: Количество публикаций: Наиболее значительные работы и результаты: The tunneling-rotation spectrum of the ground state of the hydrogen fluoride dimer, HF. HF, has been extended to the submillimeter wavelength region with the RAD-3 submillimeter spectrometer at Gorky in the frequency range 180-380 GHz at 2 10 K and pressures from 0.5 to 1.5 Torr. The spectrum has been reinvestigated at lower frequencies with a conventional Stark spectrometer at pressures between 0.1 to 0.2 Torr at the National Institute of Standards and Technology. Lines of the a-type K = 3 subband have been observed for the first time. The tunneling frequency for the K = 3 state is 114 306.35 (53) MHz. The rotational constants of this subband are somewhat anomalous as compared with those for the lower K sublevels. For example, the E rotational constant for the B, state is larger than that for the A, state, while for all the lower K sublevels the opposite is true. Higher-J R- and P-branch lines of the K = 0 through K = 2 subbands have been identified and improved rotational constants for these states have been obtained. An atlas of all a- and b-type far infrared and microwave ground state tunneling-rotation transitions for K up to 3 giving frequency, uncertainty, and relative intensity has been prepared. O.L. Polyansky, N.F. Zobov, S. Viti, J. Tennyson, P.F. Bernath, L. Wallace, Water on the sun: Line assignments based on variational calculations, Science, 277 (5324), 346-348 (1997). The infrared spectrum of hot water observed in a sunspot has been assigned. The high temperature of the sunspot (3200 K) gave rise to a highly congested pure rotational spectrum in the 10-micrometer region that involved energy levels at least halfway to dissociation. Traditional spectroscopy, based on perturbation theory, is inadequate for this problem. Instead, accurate variational solutions of the vibration-rotation Schrodinger equation were used to make assignments, revealing unexpected features, including rotational difference bands and fewer degeneracies than anticipated. These results indicate that a shift away from perturbation theory to first principles calculations is necessary in order to assign spectra of hot polyatomic molecules such as water. Zobov N.F., Polyansky O.L., Tennyson J., Shirin S.V., Nassar R., Hirao T., Imajo T., Bernath P.F., Wallace L., Using laboratory spectroscopy to identify lines in the K- and L-band spectrum of water in a sunspot, Astrophysical J., 530 (2): 994-998, (2000). The infrared spectrum of a sunspot is analyzed in the L -band region 3.1 - 4.0 mkm (2497 - 3195 cm-1) and 2.02 - 2.35 mkm (4251 - 4962 cm-1) in the K band. A new laboratory emission spectrum covering 2500 - 6000 cm-1 is analyzed to help make the assignments. Quantum number assignments are made using linelists computed using variational calculations, assisted by tabulations of experimental energy levels. There are 1207 new H216O lines assigned in the L band and 508 new lines in the K band. Vibrational band origins of 11242.8 (0.1) cm-1 and 12586(1) cm-1 are obtained for the (051) and (061) states. A. Callegari, P. Theule, R.N. Tolchenov, N.F. Zobov, O.L. Polyansky, J. Tennyson, J.S. Muenter and T.R. Rizzo, Dipole moments of highly vibrationally excited water, Science, 297, 993-995 (2002). The intensity of water absorption in the region of the solar spectrum plays a dominant role in atmospheric energy balance and hence strongly influences climate. Significant controversy exists over how to model this absorption accurately. We report dipole moment measurements of highly vibrationally excited water, which provide stringent tests of intensities determined by other means. Our measurements and accompanying calculations suggest that the best currently available potential and dipole surfaces do not accurately model intensities in the optical spectrum of water. O.L. Polyansky, A.G. Csaszar, S.V. Shirin, N.F. Zobov, P. Barletta, J. Tennyson, D.W. Schwenke and P.J. Knowles, High accuracy ab initio rotation-vibration transitions of water, Science, 299, 539-542 (2003). The spectrum of water vapor is of fundamental importance for a variety of processes, including the absorption and retention of sunlight in Earth’s atmosphere. Therefore, there has long been an urgent need for a robust and accurate predictive model for this spectrum. In our work on the high-resolution spectrum of water, we report first-principles calculations that approach experimental accuracy. To achieve this, we performed exceptionally large electronic structure calculations and considered a variety of effects, including quantum electrodynamics, which have routinely been neglected in studies of small many-electron molecules. The high accuracy of the resulting ab initio procedure is demonstrated for the main isotopomers of water. J. Tennyson, M.A. Kostin, P. Barletta, G.J. Harris, O.L. Polyansky, J. Ramanlal, N.F. Zobov, DVR3D: a Program Suite for the Calculation of Rotation-Vibration Spectra of Triatomic Molecules, Computer Physics Communications, 163, 85-116, (2004). The DVR3D program suite calculates energy levels, wavefunctions, and where appropriate dipole transition moments, for rotating and vibrating triatomic molecules. Potential energy and, where necessary, dipole surfaces must be provided. Expectation values of geometrically defined functions can be calculated, a feature which is particularly useful for fitting potential energy surfaces. The programs use an exact (within the Born–Oppenheimer approximation) Hamiltonian and offer a choice of Jacobi or Radau internal coordinates and several body-fixed axes. Rotationally excited states are treated using an efficient two-step algorithm. The programs uses a Discrete Variable Representation (DVR) based on Gauss–Jacobi and Gauss–Laguerre quadrature for all 3 internal coordinates and thus yields a fully point-wise representation of the wavefunctions. The vibrational step uses successive diagonalisation and truncation which is implemented for a number of possible coordinate orderings. The rotational, expectation value and transition dipole programs exploit the savings offered by performing integrals on a DVR grid. The new version has been rewritten in FORTRAN 90 to exploit the dynamic array allocations and the algorithm for dipole and spectra calculations have been substantially improved. New modules allow the z-axis to be embedded perpendicular to the plane of the molecule and for the calculation of expectation values. N. F. Zobov, S. V. Shirin, R. I. Ovsyannikov, O. L. Polyansky, R. J. Barber, J. Tennyson, P. F. Bernath, M. Carleer, R. Colin, P-F. Coheur, Spectrum of hot water in the 4750 – 13000 cm−1 frequency range (0.769 – 2.1 µm), Mon. Not. R. Astron. Soc., 387, 1093–1098 (2008). The high resolution laboratory spectrum of hot water vapour has been recorded in the 500–13 000 cm−1 wavenumber range and we report on the analysis of the 4750–13 000 cm−1 (0.769–2.1 μm) portion. The emission spectrum was recorded using an oxy-acetylene welding torch and a Fourier transform spectrometer. Line assignments in the laboratory spectrum as well as in an absorption spectrum of a sunspot umbra were made with the help of the BT2 line-list. Our torch spectrum is the first laboratory observation of the 9300 Å ‘steam bands’ seen in M-stars and brown dwarfs. N.F. Zobov, S.V. Shirin, L. Lodi, B.C. Silva, J. Tennyson, A.G. Csaszar, O.L. Polyansky, First-principles rotation–vibration spectrum of water above dissociation, Chem. Phys. Lett., 507, 48 – 51 (2011). High-level ab initio electronic structure and variational nuclear motion computations are combined to simulate the spectrum of the water molecule at and above its first dissociation limit. Results of these computations are compared with the related state-selective multi-photon measurements of Grechko et al. [J. Chem. Phys. 138 (2010) 081 103]. Both measured and computed spectra show pronounced structures due to quasi-bound (resonance) states. Traditional resonance features associated with trapping of vibrational or rotational energy of the system are identified and assigned. A strong and broad feature observed slightly above dissociation is found to be associated with direct photodissociation into the continuum. M. Pavanello, L. Adamowicz, A. Alijah, N.F. Zobov, I.I. Mizus, O.L. Polyansky, J. Tennyson, T. Szidarovszky, A.G. Csaszar, M. Berg, A. Petrignani, A. Wolf, Precision measurements and computations of transition energies in rotationally cold triatomic hydrogen ions up to the mid-visible spectral range, Phys. Rev. Lett., 108, 023002 (2012). First-principles computations and experimental measurements of transition energies are carried out for vibrational overtone lines of the triatomic hydrogen ion H3+ corresponding to floppy vibrations high above the barrier to linearity. Action spectroscopy is improved to detect extremely weak visible-light spectral lines on cold trapped H ions. A highly accurate potential surface is obtained from variational calculations using explicitly correlated Gaussian wave function expansions. After nonadiabatic corrections, the floppy H vibrational spectrum is reproduced at the 0.1 cm-1 level up to 16 600 cm-1. O.L. Polyansky, R.I. Ovsyannikov, A.A. Kyuberis, L. Lodi, J. Tennyson, N.F. Zobov, Calculation of rotation-vibration energy levels of the water molecule with near-experimental accuracy based on an ab initio potential energy surface, J. Phys. Chem. A. 117 (2013) 9633–9643.
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