Ovsyannikov Roman Ilyich
Research fellow of the MicroWave Spectroscopy Laboratory, PhD

2000–2006: Student at the Faculty of radiophysics, Nizhny Novgorod State University; 2006 – MS degree in Radiophysics, Faculty of radiophysics, Nizhny Novgorod State University; 2006-2009: postgraduate education, jointly supervised by IAP RAS and Bergische Universität Wuppertal (Germany),  2010 — PhD in radiophysics, thesis: Universal approach to the calculation of ro-vibrational energies for a few-atomic molecules, using potential energy surface; Supervisors: Mikhail Yu. Tretyakov and Per Jensen.

Scope of professional interests:
Theoretical spectroscopy, variational calculations, quantum chemistry.

Professional career:
2003-present: Researcher at the IAP RAS. Since 2006 some visits to Bergische Universität Wuppertal (Germany).

Awards, prizes, grants:
2000: 2nd prise in Nizhny Novgorod region olympiad in physics. 2000: 3rd prise in Nizhny Novgorod olympiad in physics. 1998: 2nd prise in Soros olympiad in physics. 2007-2009: Personal 'Rasuvaev' stipend by Nizhny Novgorod region goverment.

Pedagogical activities:
2004 – 2006: mathematics teacher in sunday school 'Radiophysic' by Nizhny Novgorod State University (for university entrants).
2004 – 2005: physics teacher, Faculty of radiophysics, Nizhny Novgorod State University.
2008 – 2011: program “Young researcher’s school” of NNC RAS, scientific advisor.

16 papers and 25 thesis

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
 modeling and analysis of rotation-vibration spectra is demonstrated by comparison with recent  measurements of Lisak and Hodges [J. Mol. Spectrosc. (unpublished??)]: assignments are given forthe seven unassigned transitions and the intensity of the strong lines are reproduced to with 3%. It  is suggested that the present procedure may be a better route to reliable line intensities than  laboratory measurements.

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).
DOI: 10.1111/j.1365-2966.2008.13234.x

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].
 Owing to an improved potential energy surface, the transition-moment results of the present work constitute a significant improvement over our previous work. The quality of the reproduction of the available experimental data suggests that we are approaching a situation where theoretical calculations of intensity information can compete with, and possibly in some cases replace, experimental determinations ofintensities for small molecules. We demonstrate that the theoretical intensity results of the present work
 are in accordance with the predictions of local-mode theory.

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
 of 1.2 cm−1 (0.7 cm−1 for J ≤ 20), which is improved to 1.0 cm−1 (0.07 cm−1 for J ≤ 20) in an  empirical adjustment of the bond lengths at the planar trans configuration. The theoretical torsional  splittings of HSOH are analyzed in terms of an existing semiempirical model for the rotation-torsion  motion. The analysis explains the irregular variation of the torsional splittings with Ka that has been  observed experimentally.

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,
Spectroscopy of H3+ based on a new high-accuracy global potential energy surface, Phil. Trans. R. Soc. A, 370, 5014-5027 (2012). DOI: 10.1098/rsta.2012.0014

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
 be obtained ab initio from the equations of quantum mechanics. Significant progress  in the computation of the ro–vibrational spectrum of H3+ is discussed. A new, global  potential energy surface (PES) based on ab initio points computed with an average  accuracy of 0.01 cm−1 relative to the non-relativistic limit has recently been constructed.  An analytical representation of these points is provided, exhibiting a standard deviation  of 0.097 cm−1 . Problems with earlier fits are discussed. The new PES is used for the  computation of transition frequencies. Recently measured lines at visible wavelengths  combined with previously determined infrared ro–vibrational data show that an accuracy  of the order of 0.1 cm−1 is achieved by these computations. In order to achieve this degree  of accuracy, relativistic, adiabatic and non-adiabatic effects must be properly accounted  for. The accuracy of these calculations facilitates the reassignment of some measured  lines, further reducing the standard deviation between experiment and theory.

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
 accuracy. A purely ab initio calculation reproduces some 200  known band origins associated with seven isotopologues of water with a standard deviation (σ) of about 0.35 cm−1.  Introducing three semiempirical scaling parameters, two affecting the BO PES and one controlling nonadiabatic effects, reducesσ  below 0.1 cm−1. Introducing one further rotational nonadiabatic parameter gives σ better than 0.1 cm−1 for all observed ro vibrational energy levels up to J = 25. We conjecture that the energy levels of closed-shell molecules with roughly the same  number of electrons as water, such as NH3, CH4, and H3O+, could be calculated to this accuracy using an analogous procedure.This means that near-ab initio calculations are capable of predicting transition frequencies with an accuracy only about a factor of  5 worse than high resolution experiments.

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.