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Ovsyannikov Roman Ilyich Education: Scope of professional interests: Professional career: Awards, prizes, grants: Pedagogical activities: Publications: Most significant papers and results: 1. R. I. Ovsyannikov and M. Yu. Tret'yakov, Determination of Loss in a Fabri--Perot Resonator from Its Response to Exciting Radiation of a Fast-Scanned Frequency, Journal of Communications Technology and Electronics, Vol. 50, No. 12, 2005, pp. 1400-1408. The response of a high-Q Fabri–Perot resonator to exciting radiation with a frequency that is fast digitally scanned and a phase that exhibits no jumps during switchings is simulated. The inverse problem of determination of the parameters of the resonator from the shape of its response is solved. Solution of the problem is important for precision measurements of the decay parameter of millimeter- and submillimeter-wave radiation in dielectrics. Such measurements have become possible with the advent of modern fast frequency synthesizers. The developed algorithm is applied to optimize the experimental conditions. 2. S.V.Shirin, O.L.Polyansky, N.F.Zobov, R.I. Ovsyannikov, A.G. Csaszar, J.Tennyson, Spectroscopically determined potential energy surfaces of the H216O, H217O and H218O Isotopologues of water, Journal of Molecular Spectroscopy 236, 216-223 (2006). Adiabatic potential energy surfaces (PESs) for three major isotopologues of water, H216O, H217O, and H218O, are constructed by fit ting to observed vibration–rotation energy levels of the system using the nuclear motion program DVR3D employing an exact kinetic energy operator. Extensive tests show that the mass-dependent ab initio surfaces due to Polyansky et al. [O.L. Polyansky, A.G. Csaszar, S.V. Shirin, N.F. Zobov, P. Barletta, J. Tennyson, D.W. Schwenke, P.J. Knowles, Science 299 (2003) 539–542.] provide an excellent starting point for the fits. The refinements are performed using a mass-independent morphing function, which smoothly distorts the original adiabatic ab initio PESs. The best overall fit is based on 1788 experimental energy levels with the rotational quantum number J = 0, 2, and 5. It reproduces these levels with a standard deviation of 0.079 cm-1 and gives, when explicit allowance is made for nonadiabatic rotational effects, excellent predictions for levels up to J = 40. Theoretical linelists for all three isotopologues of water involved in the PES construction were calculated up to 26 000 cm-1 with energy levels up to J = 10. These linelists should make an excellent starting point for spectroscopic modelling and analysis. 3. N.F. Zobov, R.I. Ovsyannikov, S.V. Shirin, O.L. Polyansky, J.Tennyson, A. Janka and P.F. Bernath, Infrared emission spectrum of hot D2O, J. Mol. Spectrosc., 240, 132-139 (2006). An emission spectrum of hot D2O (15000C) has been analyzed in the 2077-4323 cm-1 region. A considerable number of new vibration-rotation energy levels have been determined and two new vibrational levels identified. The new (041) and (022) vibrational levels have estimated band origins of 7343.93±0.01 cm-1 and 7826.38±0.02, respectively. 4. N.F. Zobov, R.I. Ovsyannikov, S.V. Shirin, O.L. Polyansky, The Assignment of Quantum Numbers in the Theoretical Spectra of the H216O, H217O, and H218O Molecules Calculated by Variational Methods in the Region 0-26000 cm-1, Optics and Spectroscopy, 102, N3, 348-353 (2007). Quantum numbers have been assigned in the theoretical spectra of three isotopologues of the water molecule: H216O, H217O, and H218O. The spectra were calculated by variational methods in the region 0– 26000 cm–1 at a temperature of 296 K. For each molecule, the quantum numbers are assigned to more than28000 levels. The quantum numbers are assigned to 216766, 210679, and 211073 spectral lines of the H216O, H217O, H218O molecules, respectively. 5. Sergei V. Shirin, Nikolay F. Zobov, Roman I. Ovsyannikov, Oleg L. Polyansky and Jonathan Tennyson,Water line lists close to experimental accuracy using a spectroscopically determined potential energy surface for H216O, H217O, and H218O, J. Chem. Phys., 128, 224306 (2008). DOI: 10.1063/1.2927903 Line lists of vibration-rotation transitions for the H216O, H217O, and H218O isotopologues of the water molecule are calculated, which cover the frequency region of 0 – 20 000 cm−1 and with rotational states up to J = 20 (J = 30 for H216O). These variational calculations are based on a new semitheoretical potential energy surface obtained by morphing a high accuracy ab initio potential using experimental energy levels. This potential reproduces the energy levels with J = 0, 2, and 5 used in the fit with a standard deviation of 0.025 cm−1. Linestrengths are obtained using an ab initio dipole moment surface. That these line lists make an excellent starting point for spectroscopic 6. Nikolai F. Zobov, Sergei V. Shirin, Roman I. Ovsyannikov, Oleg L. Polyansky, Robert J. Barber, Jonathan Tennyson, Peter F. Bernath, Michel Carleer, Reginald Colin and Pierre-François Coheur, Spectrum of hot water in the 4750 -- 13,000 cm−1 wavenumber range (0.769--2.1 µm) MNRAS, 387, 1093-1098 (2008). The high resolution laboratory spectrum of hot water vapour has been recorded in the 500– 13 000cm−1 wavenumber range and we report on the analysis of the 4750–13 000cm−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. 7. Roman I. Ovsyannikov, Walter Thiel, Sergei N. Yurchenko, Miguel Carvajal, and Per Jensen, Vibrational energies of PH3 calculated variationally at the complete basis set limit, J. Chem. Phys., 129, 044309 (2008). DOI: 10.1063/1.2956488 The potential energy surface (PES) for the electronic ground state of PH3 was calculated at the CCSD(T) level using aug-cc-pV(Q + d)Z and aug-cc-pVQZ basis sets for P and H, respectively, with scalar relativistic corrections included. A parametrized function was fitted through these ab initio points, and one parameter of this function was empirically adjusted. This analytical PES was employed in variational calculations of vibrational energies with the newly developed program TROVE. The convergence of the calculated vibrational energies with increasing vibrational basis set size was improved by means of an extrapolation scheme analogous to the complete basis set limit schemes used in ab initio electronic structure calculations. The resulting theoretical energy values are in excellent agreement with the available experimentally derived values. 8. Roman I. Ovsyannikov, Walter Thiel, Sergei N. Yurchenko, Miguel Carvajal, Per Jensen, PH3 revisited: Theoretical transition moments for the vibrational transitions below 7000 cm-1, J. Mol. Spectrosc, 252, 2, (2008) 121-128. DOI: 10.1016/j.jms.2008.07.005 We present here an extensive list of theoretical vibrational transition moments for the electronic ground state of PH3, covering all transitions with significant intensities in the wavenumber region below 7000 cm-1 . This work complements, and uses a potential energy surface from, our recent calculation of vibrational term values for PH3 [R.I. Ovsyannikov, W. Thiel, S.N. Yurchenko, M. Carvajal, P. Jensen, J. Chem. Phys. 129 (2008) 044309] and it extends, and uses a dipole moment surface from, our previous work on PH3 intensities [S.N. Yurchenko, M. Carvajal, W. Thiel, P. Jensen, J. Mol. Spectrosc. 239 (2006) 71–87]. 9. Roman I. Ovsyannikov, Vladlen V. Melnikov, Walter Thiel, Per Jensen, Oliver Baum, Thomas F. Giesen, and Sergei N. Yurchenko, Theoretical rotation-torsion energies of HSOH, J. Chem. Phys, 129, 154314 (2008). DOI: 10.1063/1.2992050 The rotation-torsion energies in the electronic ground state of HSOH are obtained in variational calculations based on a newly computed ab initio CCSD(T)/aug-cc-pV(Q + d)Z potential energy surface. Using the concept of the reaction path Hamiltonian, as implemented in the program TROVE (theoretical rovibrational energies), the rotation-vibration Hamiltonian is expanded around geometries on the torsional minimum energy path of HSOH. The calculated values of the torsionalsplittings are in excellent agreement with experiment; the root-mean-square (rms) deviation is 0.0002 cm−1 for all experimentally derived splittings (with J ≤ 40 and Ka ≤ 4). The model provides reliable predictions for splittings not yet observed. The available experimentally derived torsion-rotation term values (with J ≤ 40 and Ka ≤ 4) are reproduced ab initio with an rms deviation 10. R. I. Ovsyannikov, P. Jensen, M. Yu. Tretyakov, and S. N. Yurchenko, On the Use of the Finite Difference Method in a Calculation of Vibration–Rotation Energies , Optics and Spectroscopy , 107, № 2, с. 211–227 (2009). DOI: 10.1134/S0030400X09080104 The use of the finite difference method to obtain a Taylor series expansion of a potential energy function for a subsequent calculation of the rovibration energies of molecules is considered. A method is proposed that allows the stability of a finite difference scheme to be increased against the computational inaccuracy upon numerical expansion of a multidimensional potential energy function into a high order Taylor series. The method is based on the successive elimination of calculated expansion coefficients of a higher order in calculating the lower order coefficients by the finite difference method. The approach is illustrated for the example of the CO and H2S molecules. 11. Sergei N. Yurchenko, Roman I. Ovsyannikov, Walter Thiel, Per Jensen, Rotation–vibration energy cluster formation in XH2D and XHD2 molecules (X = Bi, P, and Sb), J. Mol. Spectrosc, 256, 119-127 (2009). DOI: 10.1016/j.jms.2009.03.001 We investigate theoretically the energy cluster formation in highly excited rotational states of several pyramidalXH2D and XHD2 molecules (X = Bi, P, and Sb) by calculating, in a variational approach, the rotational energy levels in the vibrational ground states of these species for J ≤ 70. We show that at high J thecalculated energy levels of the di-deuterated species XHD2 exhibit distinct fourfold cluster patterns highly similar to those observed for H2X molecules. We conclude from eigenfunction analysis that in the energy cluster states, the XHD2 molecule rotates about a so-called localization axis which is approximately parallel to one of the X–D bonds. For the mono-deuterated XH2D isotopologues, the rotationalspectra are found to have a simple rigid-rotor structure with twofold clusters. 12. N.F. Zobov, S.V. Shirin, R.I. Ovsyannikov, O.L. Polyansky, S.N. Yurchenko, R.J. Barber, J. Tennyson, R.J. Hargreaves, P.F. Bernath, Analysis of high temperature ammonia spectra from 780 to 2100 cm-1, J. Mol. Spectrosc, 269, 104-108 (2011). DOI: 10.1016/j.jms.2011.05.003 A recently-recorded set [Hargreaves et al., Astrophys. J., in press] of Fourier transform emission spectra of hot ammonia is analyzed using a variational line list. Approximately 3350 lines are newly assigned to mainly hot bands from vibrational states as high as v2 = 2. 431 new energy levels of these states are experimentally determined, considerably extending the range of known rotationally-excited states. Comparisons with a recent study of high J levels in the ground and first vibrational states [Yu et al., J. Chem. Phys., 133 (2010) 174317] suggests that while the line assignments presented in that work are correct, their energy level predictions suffer from problems associated with the use of very high-order perturbation series in the effective Hamiltonian. It is suggested that variational calculations provide a more stable method for analyzing spectra involving highly-excited states of ammonia. 13. Oleg L. Polyansky, Alexander Alijah, Nikolai F. Zobov, Irina I. Mizus, Roman I. Ovsyannikov, Jonathan Tennyson, Lorenzo Lodi, Tamas Szidarovsky, Attila G. Császár, The molecular ion H3+ is the simplest polyatomic and poly-electronic molecular system, and its spectrum constitutes an important benchmark for which precise answers can 14. Oleg L. Polyansky, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Lorenzo Lodi, Jonathan Tennyson, Nikolai F. Zobov, Calculation of Rotation-vibration Energy Levels of the Water Molecule with Near-Experimental Accuracy Based on an ab Initio Potential Energy Surface, The Journal of Physical Chemistry A, 2013, 117 (39), 9633–9643. DOI: 10.1021/jp312343z A recently computed, high-accuracy ab initio Born−Oppenheimer (BO) potential energy surface (PES) for the water molecule is combined with relativistic, adiabatic, quantum electrodynamics, and, crucially, nonadiabatic corrections. Calculations of ro-vibrational levels are presented for several water isotopologues and shown to have unprecedented 15. Oleg L. Polyansky, Igor N. Kozin, Roman I. Ovsyannikov, Pawel Malyszek, Jacek Koput, Jonathan Tennyson, and Sergei N. Yurchenko, Variational Calculation of Highly Excited Rovibrational Energy Levels of H2O2, The Journal of Physical Chemistry A, 2013, 117 (32), 7367–7377. DOI: 10.1021/jp401216g Results are presented for highly accurate ab initio variational calculation of the rotation - vibration energy levels of H2O2 in its electronic ground state. These results use a recently computed potential energy surface and the variational nuclear-motion programmes WARV4, which uses an exact kinetic energy (EKE) operator, and TROVE, which uses a numerical expansion for the kinetic energy. The TROVE calculations are performed for levels with high values of rotational excitation, J up to 35. The purely ab initio calculations of the rovibrational energy levels reproduce the observed levels with a standard deviation of about 1 cm−1,similar to that of the J = 0 calculation as the discrepancy between theory and experiment for rotational energies within a given vibrational state is substantially determined by the error in the vibrational band origin. Minor adjustments are made to the ab initio equilibrium geometry and to the height of the torsional barrier. Using these and correcting the band origins using the error in J = 0 states lowers the standard deviation of the observed − calculated energies to only 0.002 cm−1 for levels up to J = 10 and 0.02 cm−1 for all experimentally know energy levels, which extend up to J = 35. 16. Roman I. Ovsyannikov, Tsuneo Hirano, and Per Jensen, The Renner Effect in the X? 2A″ and Ã2A′ Electronic States of HSO/HOS, The Journal of Physical Chemistry A, (2013). DOI: 10.1021/jp406940w We report a theoretical investigation of the X?2A″ and Ã2A' electronic states of HSO/HOS. Three-dimensional potential energy surfaces for the X?2A″ and Ã2A' electronic states of HSO/HOS have been calculated ab initio by the core-valence MR-SDCI+Q/[aug-cc-pCVQZ(S,O),aug-cc-pVQZ(H)] method, and near-global potential energy surfaces have been constructed. These surfaces have been used, in conjunction with our computer program DR, for calculating HSO/HOS rovibronic energies in the electronic states X?2A″ and Ã2A'. Both electronic states have nonlinear equilibrium geometries and they correlate with 2Π states at the H-S-O and H-O-S linear configurations so that they exhibit the double Renner effect. The present DR calculation of the rovibronic energies for the X?2A″ and Ã2A' electronic states of HSO/HOS is complicated by the Renner-interaction breakdown of the Born-Oppenheimer approximation and by HSO/HOS isomerization. Calculated energies are reported together with analyses of the rovibronic wave functions for selected states. These analyses explore the interplay between the effects of, on one hand, Renner interaction and, on the other hand, isomerization tunneling in the rovibronic dynamics of HSO/HOS.
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