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Biological and Chemical Physics

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Ultraviolet Photodissociation Of Ocs: Product Energy And Angular Distributions, George C. Mcbane, Johan A. Schmidt, M. S. Johnson, Reinhard Schinke Mar 2013

Ultraviolet Photodissociation Of Ocs: Product Energy And Angular Distributions, George C. Mcbane, Johan A. Schmidt, M. S. Johnson, Reinhard Schinke

Peer Reviewed Articles

The ultraviolet photodissociation of carbonyl sulfide (OCS) was studied using three-dimensional potential energy surfaces and both quantum mechanical dynamics calculations and classical trajectory calculations including surface hopping. The transition dipole moment functions used in an earlier study [J. A. Schmidt, M. S. Johnson, G. C. McBane, and R. Schinke, J. Chem. Phys. 137, 054313 (2012)] were improved with more extensive treatment of excited electronic states. The new functions indicate a much larger contribution from the 1 1A" state (1Σ- in linear OCS) than was found in the previous work. The new transition dipole functions yield absorption spectra that ...


The Ultraviolet Spectrum Of Ocs From First Principles: Electronic Transitions, Vibrational Structure And Temperature Dependence, Johan A. Schmidt, M. S. Johnson, George C. Mcbane, Reinhard Schinke Aug 2012

The Ultraviolet Spectrum Of Ocs From First Principles: Electronic Transitions, Vibrational Structure And Temperature Dependence, Johan A. Schmidt, M. S. Johnson, George C. Mcbane, Reinhard Schinke

Peer Reviewed Articles

Global three dimensional potential energy surfaces and transition dipole moment functions are calculated for the lowest singlet and triplet states of carbonyl sulfide at the multireference configuration interaction level of theory. The first ultraviolet absorption band is then studied by means of quantum mechanical wave packet propagation. excitation of the repulsive 21A' state gives the main contribution to the cross section. Excitation of the repulsive 11A" state is about a factor of 20 weaker at the absorption peak (Eph ≈ 45 000 cm-1) but becomes comparable to the 21A' state absorption with decreasing ...


Multi-State Analysis Of The Ocs Ultraviolet Absorption Including Vibrational Structure, Johan A. Schmidt, M. S. Johnson, George C. Mcbane, Reinhard Schinke Apr 2012

Multi-State Analysis Of The Ocs Ultraviolet Absorption Including Vibrational Structure, Johan A. Schmidt, M. S. Johnson, George C. Mcbane, Reinhard Schinke

Peer Reviewed Articles

The first absorption band of OCS (carbonyl sulfide) is analyzed using potential energy surfaces and transition dipole moment functions of the lowest four singlet and the lowest four triplet states. Excitation of the 21A' state is predominant except at very low photon energies. It is shown that the vibrational structures in the center of the band are due to excitation of the 23A" triplet state, whereas the structures at the very low energies are caused by bending excitation in the potential wells of states 21A' and 11A".


Product Angular Distributions In The Ultraviolet Photodissociation Of N2O, George C. Mcbane, Reinhard Schinke Jan 2012

Product Angular Distributions In The Ultraviolet Photodissociation Of N2O, George C. Mcbane, Reinhard Schinke

Peer Reviewed Articles

The angular distribution of products from the ultraviolet photodissociation of nitrous oxide yielding O(1D) and N2(X1Σ+g) was investigated using classical trajectory calculations. The calculations modeled absorption only to the 21A'electronic state but used surface-hopping techniques to model nonadiabatic transitions to the ground electronic state late in the dissociation. Observed values of the anisotrophy parameter β, which decrease as the product N2 rotational quantum number jincreases, could be well reproduced. The relatively low observed βvalues arise principally from nonaxial recoil due to the very strong bending forces present ...


Photodissociation Of N2O: Energy Partitioning, Johan A. Schmidt, M. S. Johnson, U. Lorenz, George C. Mcbane, Reinhard Schinke Jul 2011

Photodissociation Of N2O: Energy Partitioning, Johan A. Schmidt, M. S. Johnson, U. Lorenz, George C. Mcbane, Reinhard Schinke

Peer Reviewed Articles

The energy partitioning in the UV photodissociation of N2O is investigated by means of quantum mechanical wave packet and classical trajectory calculations using recently calculated potential energy surfaces. Vibrational excitation of N2 is weak at the onset of the absorption spectrum, but becomes stronger with increasing photon energy. Since the NNO equilibrium angles in the ground and the excited state differe by about 70°, the molecule experiences an extraordinarily large torque during fragmentation producing N2in very high rotational states. The vibrational and rotational distributions obtained from the quantum mechanical and the classical calculations agree remarkably ...


Mapping Water Collisions For Interstellar Space Conditions, C.-H. Yang, G. Sarma, J. J. Ter Meulen, D. H. Parker, George C. Mcbane, Laurent Wiesenfeld, A. Faure Oct 2010

Mapping Water Collisions For Interstellar Space Conditions, C.-H. Yang, G. Sarma, J. J. Ter Meulen, D. H. Parker, George C. Mcbane, Laurent Wiesenfeld, A. Faure

Peer Reviewed Articles

We report a joint experimental and theoretical study that directly tests the quality of the potential energy surfaces used to calculate energy changing cross sections of water in collision with helium and molecular hydrogen, at conditions relevant for astrophysics. Fully state-to-state differential cross sections are measured for H2O-He and H2O-H2 collisions at 429 and 575 cm-1 collision energy, respectively. We compare these differential cross sections with theoretical ones for H2O+H2 derived from state-of-the-art potential energy surfaces [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)] and quantum scattering calculations ...


Photodissociation Of Ozone In The Hartley Band: Potential Energy Surfaces, Nonadiabatic Couplings, And Singlet/Triplet Branching Ratio, Reinhard Schinke, George C. Mcbane Jan 2010

Photodissociation Of Ozone In The Hartley Band: Potential Energy Surfaces, Nonadiabatic Couplings, And Singlet/Triplet Branching Ratio, Reinhard Schinke, George C. Mcbane

Peer Reviewed Articles

The lowest five 1A'states of ozone, involved in the photodissociation with UV light, are analyzed on the basis of multireference configuration interaction electronic structure calculations with emphasis on the various avoided crossings in different regions of coordinate space. Global diabatic potential energy surfaces are constructed for the lowest four states termed X, A, B, and R. In addition, the off-diagonal potentials that couple the initially excited state B with states R and A are constructed to reflect results from additional electronic structure calculations, including the calculation of nonadiabatic coupling matrix elements. The A/X and A/R couplings ...


Production Of O2 Herzberg States In The Deep Uv Photodissociation Of Ozone, Reinhard Schinke, George C. Mcbane, L. Shen, P. C. Singh, A. G. Suits Jul 2009

Production Of O2 Herzberg States In The Deep Uv Photodissociation Of Ozone, Reinhard Schinke, George C. Mcbane, L. Shen, P. C. Singh, A. G. Suits

Peer Reviewed Articles

High-resolution imaging experiments combined with new electronic structure and dynamics calculations strongly indicate that the O(3P)+O2 products with very low kinetic energy release (Etr<0.2 eV) formed in the deep UV (226 nm) photodissociation of ozone reflect excitation of the Herzberg states of O2: A' 3Δu(v=0, 1, 2) and A 3Σ+u(v=0, 1). This interpretation contradicts the earlier assignment to very high (v≥26) vibrational states of O2(3Σ-g).


An Exchange-Coulomb Model Potential Energy Surface For The Ne-Co Interaction. I. Calculation Of Ne-Co Van Der Waals Spectra, Ashok K. Dham, Frederick R. W. Mccourt, William J. Meath, George C. Mcbane Jun 2009

An Exchange-Coulomb Model Potential Energy Surface For The Ne-Co Interaction. I. Calculation Of Ne-Co Van Der Waals Spectra, Ashok K. Dham, Frederick R. W. Mccourt, William J. Meath, George C. Mcbane

Peer Reviewed Articles

Exchange-Coulomb model potential energy surfaces have been developed for the Ne–CO interaction. The initial model is a three-dimensional potential energy surface based upon computed Heitler–London interaction energies and literature results for the long-range induction and dispersion energies, all as functions of interspecies distance, the orientation of CO relative to the interspecies axis, and the bond length of the CO molecule. Both a rigid-rotor model potential energy surface, obtained by setting the CO bond length equal to its experimental spectroscopic equilibrium value, and a vibrationally averaged model potential energy surface, obtained by averaging the stretching dependence over the ground ...


Exploring Renner-Teller Induced Quenching In The Reaction H(2S)+Nh(A1Δ): A Combined Experimental And Theoretical Study, L. Adam, W. Hack, George C. Mcbane, H. Zhu, Z.-W. Qu, Reinhard Schinke Jan 2007

Exploring Renner-Teller Induced Quenching In The Reaction H(2S)+Nh(A1Δ): A Combined Experimental And Theoretical Study, L. Adam, W. Hack, George C. Mcbane, H. Zhu, Z.-W. Qu, Reinhard Schinke

Peer Reviewed Articles

Experimental rate coefficients for the removal of NH(a1Δ) and ND(a1Δ) in collisions with H and D atoms are presented; all four isotope combinations are considered: NH+H, NH+D, ND+H, and ND+D. The experiments were performed in a quasistatic laser-flash photolysis/laser-induced fluorescence system at low pressures. NH(a1Δ) and ND(a1Δ) were generated by photolysis of HN3 and DN3, respectively. The total removal rate coefficients at room temperature are in the range of (3-5) x 1013 cm3 mol-1 s-1. For two ...


A Hierarchical Family Of Three-Dimensional Potential Energy Surfaces For He-Co, Kirk A. Peterson, George C. Mcbane Aug 2005

A Hierarchical Family Of Three-Dimensional Potential Energy Surfaces For He-Co, Kirk A. Peterson, George C. Mcbane

Peer Reviewed Articles

A hierarchical family of five three-dimensional potential energy surfaces has been developed for the benchmark He-CO system. Four surfaces were obtained at the coupled cluster singles and doubles level of theory with a perturbational estimate of triple excitations, CCSD(T), and range in quality from the doubly augmented double-zeta basis set to the complete basis set (CBS) limit. The fifth corresponds to an approximate CCSDT/CBS surface (CCSD with iterative triples/CBS, denoted CBS+corr). The CBS limit results were obtained by pointwise basis set extrapolations of the individual counterpoise-corrected interaction energies. For each surface, over 1000 interaction energies were ...


State-To-State Rotational Relaxation Rate Constants For Co+Ne From Ir-Ir Double-Resonance Experiments: Comparing Theory To Experiment, David A. Hostutler, Tony C. Smith, Gordon D. Hager, George C. Mcbane, Michael C. Heaven Jan 2004

State-To-State Rotational Relaxation Rate Constants For Co+Ne From Ir-Ir Double-Resonance Experiments: Comparing Theory To Experiment, David A. Hostutler, Tony C. Smith, Gordon D. Hager, George C. Mcbane, Michael C. Heaven

Peer Reviewed Articles

IR-IR double-resonance experiments were used to study the state-to-state rotational relaxation of CO with Ne as a collision partner. Rotational levels in the range Ji=2-9 were excited and collisional energy transfer of population to the levels Jf=2-8 was monitored. The resulting data set was analyzed by fitting to numerical solutions of the master equation. State-to-state rate constant matrices were generated using fitting law functions. Fitting laws based on the modifed exponential gap (MEG) and statistical power exponential gap (SPEG) models were used; the MEG model performed better than the SPEG model. A rate constant matrix was ...


State-To-State Rotational Rate Constants For Co+He: Infrared Double Resonance Measurements And Simulation Of The Data Using The Sapt Theoretical Potential Energy Surface, Tony C. Smith, David A. Hostutler, Gordon D. Hager, Michael C. Heaven, George C. Mcbane Nov 2003

State-To-State Rotational Rate Constants For Co+He: Infrared Double Resonance Measurements And Simulation Of The Data Using The Sapt Theoretical Potential Energy Surface, Tony C. Smith, David A. Hostutler, Gordon D. Hager, Michael C. Heaven, George C. Mcbane

Peer Reviewed Articles

An extensive data set of 54 time-resolved pump-probe measurements was used to examine CO+He rotational energy transfer within the CO v=2 rotational manifold. Rotational levels in the range Ji=2-9 were excited and collisional energy transfer of population to the levels Jf=1-10 was monitored. The resulting data set was analyzed by fitting to numerical solutions of the master equation. State-to-state rate constant matrices were generated using fitting law functions and ab initio theoretical calculations that employed the SAPT potential energy surface of Heijmen et al. [J. Chem. Phys. 107, 9921 (1997)]. Fitting laws based on ...


Interaction Second Virial Coefficients From A Recent H2-Co Potential Energy Surface, J. Gottfried, George C. Mcbane Dec 1999

Interaction Second Virial Coefficients From A Recent H2-Co Potential Energy Surface, J. Gottfried, George C. Mcbane

Peer Reviewed Articles

No abstract provided.


State-To-State Rotational Excitation Of Co By H2 Near 1000 Cm-1 Collision Energy, Stiliana Antonova, Antonis P. Tsakotellis, Ao Lin, George C. Mcbane Oct 1999

State-To-State Rotational Excitation Of Co By H2 Near 1000 Cm-1 Collision Energy, Stiliana Antonova, Antonis P. Tsakotellis, Ao Lin, George C. Mcbane

Peer Reviewed Articles

Relative state-to-state rotationally inelastic cross sections for excitation of carbon monoxide by hydrogen were measured in a crossed molecular beam experiment at collision energies 795, 860, and 991 cm-1. The results are compared to predictions of a recent ab initio potential energy surface [J. Chem. Phys. 108, 3554 (1998)]. The agreement is very good. A comparison with older data on thermally averaged total depopulation cross sections [Chem. Phys. 53, 165 (1980)] indicates that the absolute magnitudes of the cross sections predicted by the surface are too high. The CO excitation is dominated by collisions that are elastic in H ...


State To State Ne-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane Mar 1999

State To State Ne-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane

Peer Reviewed Articles

Measurements of state-to-state integral cross sections for rotational excitation of CO by collisions with Ne are reported. The measurements were performed in crossed molecular beams with resonance enhanced multiphoton detection at collision energies of 711 and 797 cm-1. The cross sections display strong interference structure, with a propensity for odd Δj below Δj=10. Predictions of the ab initio potential surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)] and the new ab initio surface of McBane and Cybulski [J. Chem. Phys. 110, 11734 (1999), preceding paper] are compared to the data. The new ...


An Ab Initio Potential Energy Surface For The Ne-Co, George C. Mcbane, Slawomir M. Cybulski Mar 1999

An Ab Initio Potential Energy Surface For The Ne-Co, George C. Mcbane, Slawomir M. Cybulski

Peer Reviewed Articles

A new ab initio two-dimensional potential energy surface for the Ne-CO interaction is described. The surface was obtained by the supermolecule method at the CCSD(T) level of theory. It is compared with several experimental data sets and with the symmetry-adapted perturbation theory (SAPT) surface of Moszynski et al. [J. Phys. Chem. A 101, 4690 (1997)]. The new surface gives modestly better predictions of experimental results that depend on close approach of Ne to CO, but does not describe the ground state geometry as well as the SAPT surface.


State To State He-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane Oct 1998

State To State He-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane

Peer Reviewed Articles

Relative integral cross sections for rotational excitation of CO in collisions with He were measured at energies of 72 and 89 meV. The cross sections are sensitive to anisotrophy in the repulsive wall of the He-CO interaction. The experiments were done in crossed molecular beams with resonance enhanced multiphoton ionization detection. The observed cross sections display interference structure at low Δj, despite the average over the initial CO rotational distribution. At higher Δj, the cross sections decrease smoothly. The results are compared with cross sections calculated from two high quality potential energy surfaces for the He-CO interaction. The ...


Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry Nov 1993

Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry

Peer Reviewed Articles

No abstract provided.


Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry Mar 1993

Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Because of the extremely small binding energy of the helium dimer, the nuclear wave function is delocalized over an extremely large range of separations. One might therefore expect the properties of this extraordinary species to be sensitive to the potential at very large internuclear distances, r, where relativistic corrections to the usual van der Waals interaction may be important. We have estimated the effect of retardation, which changes the r-6 dependence of the potential to r-7 in the limit of large r, and have found that the binding energy and expectation value (r) are indeed significantly affected by ...


The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry Dec 1992

The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Helium dimer ion was observed after electron impact ionization of a supersonic expansion of helium with translational temperature near 1 mK. The dependence of the ion signal on source pressure, distance from the source, and electron kinetic energy was measured. The signal was determined to arise from ionization of neutral helium dimer.


Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz Oct 1990

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz

Peer Reviewed Articles

Vibrational and rotational distributions of CO excited by collisions with 2.3 eV H atoms have been obtained by monitoring the products with vacuum ultraviolet (VUV) laser induced fluorescence. Translational-to-vibrational (T→V) transfer is dominated by the dynamics of collisions occurring in the two wells on the H+CO potential energy surface, one characterizing the HCO radical and the other characterizing COH. The measured vibrational distributions agree well with the results of trajectory calculations performed on the ab initio potential energy surface of Bowman, Bittman, and Harding (BBH). The measured rotational distributions show two significant differences from the calculated ones ...


The 157 Nm Photodissociation Of Ocs, C. E. Strauss, George C. Mcbane, P. L. Houston, I. Burak, J. W. Hepburn Jan 1989

The 157 Nm Photodissociation Of Ocs, C. E. Strauss, George C. Mcbane, P. L. Houston, I. Burak, J. W. Hepburn

Peer Reviewed Articles

The photodissociation of OCS at 157 nm has been investigated by using tunable vacuum ultraviolet radiation to probe the CO and S photoproducts. Sulfur is produced almost entirely in the 1S state, while CO is produced in its ground electronic state and in vibrational levels from v=0-3 in the appropriate ratio (v=0):(v=1):(v=2):(v=3) = (1.0):(1.0):(0.5):(0.3). The rotational distribution for each vibrational level is found to be near Boltzmann, with temperatures that decrease from 1350 K for v=0 to 780 K for v=3. Measurements of ...


State-Selective Studies Of T→R, V Energy Transfer: The H+Co System, G. K. Chawla, George C. Mcbane, P. L. Houston, G. C. Schatz Dec 1987

State-Selective Studies Of T→R, V Energy Transfer: The H+Co System, G. K. Chawla, George C. Mcbane, P. L. Houston, G. C. Schatz

Peer Reviewed Articles

Collisional energy transfer from H atoms to CO(v=0, J≈2) has been studied at a collision energy of 1.58±0.07 eV by photolyzing H2S at 222 nm in a nozzle expansion with CO and probing the CO(v", J") levels using tunable VUV laser-induced fluorescence. The ratio CO(v"=1)/CO(v"=0) is found to be 0.1±0.008. The rotational distribution of CO(v"=0) peaks at J"<11 and decays gradually; population is still observed at J">45. The rotational distribution of CO(v"=1) is broad and peaks near J"=20. The experimental results are compared to quasiclassical ...