P. R. Bunker

Publications (100)155.77 Total impact

• Conference Proceeding: The Renner Effect in Triatomic Molecules

  P. R. Bunker, W. P. Kraemer, T. Hirano, Per Jensen
  [show abstract] [hide abstract]
  ABSTRACT: To calculate the rovibronic energies of a triatomic molecule in an electronic state that is degenerate at linear nuclear configurations, it is necessary to allow for the breakdown of the Born-Oppenheimer approximation. This is because the electronic degeneracy is resolved at bent configurations and there is a nonnegligible coupling between the two states caused by molecular rotation. This is termed the Renner (or Renner-Teller) effect. To calculate the rovibronic term values and wavefunctions in this situation, we have developed a variational computational procedure and we have included the effect of spin-orbit coupling for nonsinglet states. The wavefunctions can be used to predict and interpret the results of Coulomb explosion imaging experiments. We can also calculate spectral line intensities so that absorption and emission spectra can be simulated. We review the work and our application to the CH+2 and FeOH molecules.
  International Conference of Computational Methods in Sciences and Engineering 2009; 01/2012
• Article: The predicted infrared spectrum of the hypermetallic molecule CaOCa in its lowest two electronic states X1Σg+and a3Σu+

  B. Ostojić, P. R. Bunker, P. Schwerdtfeger, A. Gertych, Per Jensen
  [show abstract] [hide abstract]
  ABSTRACT: This study of CaOCa is our third paper in a series on Group 2 alkaline-earth M2O hypermetallic oxides. As with our previous calculations for BeOBe and MgOMg, the ab initio calculations we report here show that CaOCa has a linear 1Rþg ground electronic state and a very low lying linear ~a3Rþu first excited triplet electronic state. For CaOCa we determine that the singlet–triplet splitting Teð~aÞ ¼ 386 cm�1.We calculate the three-dimensional potential energy surface, and the electric dipole moment surfaces, of each of the two states using a multireference configuration interaction (MRCISD) approach in combination with internally contracted multireference perturbation theory (RS2C) based on full-valence complete active space self-consistent field (FV-CASSCF) wavefunctions with a cc-pwCVQZ-DK basis set for Ca and a cc-pCVQZ basis set for O. We simulate the infrared absorption spectra of 40Ca16O40Ca in each of these electronic states in order to aid in its eventual spectroscopic characterization.
  Journal of Molecular Structure 01/2012; 1023:101. · 1.63 Impact Factor
• Article: The predicted spectrum of the hypermetallic molecule MgOMg.

  B Ostojić, P R Bunker, P Schwerdtfeger, B Assadollahzadeh, Per Jensen
  [show abstract] [hide abstract]
  ABSTRACT: The present study of MgOMg is a continuation of our theoretical work on Group 2 M(2)O hypermetallic oxides. Previous ab initio calculations have shown that MgOMg has a linear (1)Σ(g)+ ground electronic state and a very low lying first excited triplet electronic state that is also linear; the triplet state has (3)Σ(u)+ symmetry. No gas phase spectrum of this molecule has been assigned, and here we simulate the infrared absorption spectrum for both states. We calculate the three-dimensional potential energy surface, and the electric dipole moment surfaces, of each of the two states using a multireference configuration interaction (MRCISD) approach based on full-valence complete active space self-consistent field (FV-CASSCF) wavefunctions with a cc-pCVQZ basis set. A variational MORBID calculation using our potential energy and dipole moment surfaces is performed to determine rovibrational term values and to simulate the infrared absorption spectrum of the two states. We also calculate the dipole polarizability of both states at their equilibrium geometry in order to assist in the interpretation of future beam deflection experiments. Finally, in order to assist in the analysis of the electronic spectrum, we calculate the vertical excitation energies, and electric dipole transition matrix elements, for six excited singlet states and five excited triplet states using the state-average full valence CASSCF-MRCISD/aug-cc-pCVQZ procedure.
  Physical Chemistry Chemical Physics 03/2011; 13(16):7546-53. · 3.57 Impact Factor
• Article: Erratum: Communications: Evidence for proton tunneling from the microwave spectrum of the formic acid: Propriolic acid dimer [J. Chem. Phys. 132, 201101 (2010)].

  Adam M Daly, P R Bunker, Stephen G Kukolich
  The Journal of chemical physics 08/2010; 133(7):079903. · 3.09 Impact Factor
• Article: Communications: Evidence for proton tunneling from the microwave spectrum of the formic acid-propriolic acid dimer.

  Adam M Daly, P R Bunker, Stephen G Kukolich
  [show abstract] [hide abstract]
  ABSTRACT: The microwave spectrum of the formic acid-propriolic acid dimer was measured in the 5-13 GHz range using a pulsed-beam, Fourier transform spectrometer. 22 a-dipole rotational transitions and 3 b-dipole rovibrational transitions were measured for the normal isotopomer. All of these observed transitions were split into doublets by the effects of the concerted tunneling of the two acid protons. The smaller splittings of 1-1.5 MHz for the a-dipole transitions are due to the differences in rotational constants for the upper and lower tunneling states. The b-dipole transitions are rovibrational (combination) transitions with a change in rotational state and tunneling state and provide direct information on the tunneling splittings since these observed splittings are the sum of the tunneling level splittings for the two rotational states involved in the transition. The b-dipole splittings are 55.16(0(00)-1(11)), 58.58(1(01)-2(12)), and 71.24 MHz(2(02)-3(13)). No similar splittings were observed when deuterium was substituted for either or both of the hydrogen bonding protons. For the lower tunneling state (nu(0) (+)), A=5988.7(7), B=927.782(7), and C=803.720(7) MHz. For the upper tunneling state (nu(0) (-)), A=5988(1), B=927.78(1), and C=804.06(1) MHz. Using a simple model with potential function V=ax(4)-bx(2) the splittings could be reproduced reasonably well with a barrier height of H(e)=3800 cm(-1).
  The Journal of chemical physics 05/2010; 132(20):201101. · 3.09 Impact Factor
• Article: The predicted infrared spectrum of the hyperberyllium molecule BeOBe in its X1Σg+and a3Σu+ electronic states

  B. Ostojić, Per Jensen, P. Schwerdtfeger, B. Assadollahzadeh, P. R. Bunker
  Journal of Molecular Spectroscopy 01/2010; 263:21. · 1.51 Impact Factor
• Article: The Predicted Spectrum of FeOH in Its Renner-degenerate X6A' and Ã6A'' Electronic States

  T. Hirano, P. R. Bunker, S. Patchkovskii, U. Nagashima, Per Jensen
  Journal of Molecular Spectroscopy 01/2009; 256:45. · 1.51 Impact Factor
• Chapter: Spectroscopy and Broken Symmetry

  P. R. Bunker, Per Jensen
  01/2008: pages 321-346; , ISBN: 978-0-444-53175-9
• Source

  Available from: Per Jensen

  Article: New potential energy surfaces for the X and A states of CH2+

  P. R. Bunker, W. P. Kraemer, S. N. Yurchenko, W. Thiel, C. F. Neese, J. L. Gottfried, Per Jensen
  Molecular Physics 01/2007; 105:1369. · 1.82 Impact Factor
• Article: The rovibronic energies of the SiNSi radical in its X²Πg electronic state

  P. R. Bunker, R. Guérout, Z. J. Jakubek, Per Jensen, S. N. Yurchenko
  [show abstract] [hide abstract]
  ABSTRACT: We present the results of a calculation of the rovibronic energies of the SiNSi radical in its X²Πg electronic ground state. At bent geometries, the electronic degeneracy is split to give a lower state of A2 symmetry and an upper state of B2 symmetry; each state is linear at equilibrium. The rovibronic calculation involves consideration of the Renner effect, and we initially made the calculation using ab initio A2 and B2 potential surfaces. The term values obtained were of help in making vibronic assignments in a newly obtained spectrum of the molecule. Having vibronically assigned the spectrum, we refined the potentials in a fitting to the vibronic term value separations. The optimized potentials allow us, in principle, to predict all rovibronic energies of the X²Πg state.
  Journal of Molecular Structure 05/2006; 795:9-13. · 1.63 Impact Factor
• Article: A dispersed fluorescence and ab initio investigation of the X2B1 and A2A1 electronic states of the PH2 molecule.

  Z J Jakubek, P R Bunker, M Zachwieja, S G Nakhate, B Simard, S N Yurchenko, W Thiel, Per Jensen
  [show abstract] [hide abstract]
  ABSTRACT: In this work, the X2B1 and A2A1 electronic states of the phosphino (PH2) free radical have been studied by dispersed fluorescence and ab initio methods. PH2 molecules were produced in a molecular free-jet apparatus by laser vaporizing a silicon rod in the presence of phosphine (PH3) gas diluted in helium. The laser-induced fluorescence, from the excited A2A1 electronic state down to the ground electronic state, was dispersed and analyzed. Ten (upsilon1upsilon2upsilon3) vibrationally excited levels of the ground electronic state, with upsilon1 < or = 2, upsilon2 < or = 6, and upsilon3 = 0, have been observed. Ab initio potential-energy surfaces for the X2B1 and A2A1 electronic states have been calculated at 210 points. These two states correlate with a 2Pi(u) state at linearity and they interact by the Renner-Teller coupling and spin-orbit coupling. Using the ab initio potential-energy surfaces with our RENNER computer program system, the vibronic structure and relative intensities of the A2A1 --> X2B1 emission band system have been calculated in order to corroborate the experimental assignments.
  The Journal of Chemical Physics 04/2006; 124(9):94306. · 3.33 Impact Factor
• Source

  Available from: jakubek.net

  Article: A dispersed fluorescence and ab initio investigation of the X̃²B₁ and òA₁ electronic states of the PH₂ molecule

  Z. J. Jakubek, P. R. Bunker, M. Zachwieja, S. G. Nakhate, B. Simard, S. N. Yurchenko, W. Thiel, Per Jensen
  [show abstract] [hide abstract]
  ABSTRACT: In this work, the X̃²B₁ and òA₁ electronic states of the phosphino (PH₂) free radical have been studied by dispersed fluorescence and ab initio methods. PH₂ molecules were produced in a molecular free-jet apparatus by laser vaporizing a silicon rod in the presence of phosphine (PH₃) gas diluted in helium. The laser-induced fluorescence, from the excited òA₁ electronic state down to the ground electronic state, was dispersed and analyzed. Ten (v₁v₂v₃) vibrationally excited levels of the ground electronic state, with v₁≤2, v₂≤6, and v₃=0, have been observed. Ab initio potential-energy surfaces for the X̃²B₁ and òA₁ electronic states have been calculated at 210 points. These two states correlate with a ²Π�u state at linearity and they interact by the Renner-Teller coupling and spin-orbit coupling. Using the ab initio potential-energy surfaces with our RENNER computer program system, the vibronic structure and relative intensities of the òA₁→X̃²B₁ emission band system have been calculated in order to corroborate the experimental assignments.
  The Journal of Chemical Physics 03/2006; 124(9):094306. · 3.33 Impact Factor
• Article: A calculation of the rovibronic energies and spectrum of the B1A1 electronic state of SiH2.

  R Guérout, P R Bunker, Per Jensen, W P Kraemer
  [show abstract] [hide abstract]
  ABSTRACT: The B1A1 electronic state of silylene (SiH2) is the second excited singlet state of the molecule and, like the analogous c state of methylene (CH2), it is quasilinear with symmetry 1sigmag+ at linearity. This state dissociates to Si(1D) + H2(1sigmag+). At equilibrium, the B state of SiH2 has an energy that we calculate to be 0.71 eV above that of the dissociation products. However, there is a barrier to dissociation that allows quasibound rovibrational levels to occur, and some have been observed recently [Y. Muramoto et al., J. Chem. Phys. 122, 154302 (2005)]. Starting with our analytical ab initio potential-energy surface, we adjusted it in a fitting to the experimental term values in order to determine the optimum potential-energy function in the bound region. This potential has a C2v equilibrium structure with a SiH bond length of 1.459 angstroms and a bond angle of 165.4 degrees; the barrier to linearity is only 129 cm(-1). Using the optimized potential-energy surface we calculate B-state term values, and using our calculated y and z dipole moment surfaces, we simulate the rotation-vibration spectrum of the state in order to assist in the detection of the matrix isolation spectrum.
  The Journal of Chemical Physics 01/2006; 123(24):244312. · 3.33 Impact Factor
• Article: Rotation-vibration energy level clustering in the X2B1 ground electronic state of PH2

  S. N. Yurchenko, W. Thiel, Per Jensen, P. R. Bunker
  Journal of Molecular Spectroscopy 01/2006; 239:160. · 1.51 Impact Factor
• Chapter: Symmetry and Broken Symmetry in Molecules

  P.R. Bunker, Per Jensen
  01/2005;
• Article: A calculation of the rovibronic energies and spectrum of the B1A1 electronic state of SiH2

  R. Guérout, P. R. Bunker, Per Jensen, W.P. Kraemer
  The Journal of Chemical Physics 01/2005; 123(244312). · 3.33 Impact Factor
• Article: Coulomb Explosion Imaging: The CH3+ and H3O+ Molecules

  S. N. Yurchenko, P. R. Bunker, Per Jensen
  Journal of Molecular Structure 01/2005; 742:43. · 1.63 Impact Factor
• Article: The spectrum of singlet SiH2

  S. N. Yurchenko, P. R. Bunker, W. P. Kraemer, Per Jensen
  Canadian Journal of Chemistry 01/2004; 82:694. · 1.24 Impact Factor
• Article: Chirality in Rotational Energy Level Clusters

  P. R. Bunker, Per Jensen
  Journal of Molecular Spectroscopy 01/2004; 228:640. · 1.51 Impact Factor
• Book: Fundamentals of Molecular Symmetry

  P. R. Bunker, Per Jensen
  1st 01/2004; IOP Publishing.