Showing papers by "Jonathan Tennyson published in 2001"
TL;DR: Experimentally derived energy levels for 12, 248 vibration-rotation states of the H2 16O isotopomer of water, more than doubling the number in previous, disparate, compilations are presented in this article.
Abstract: Experimentally derived energy levels are presented for 12 248 vibration–rotation states of the H2 16O isotopomer of water, more than doubling the number in previous, disparate, compilations. For each level an error and reference to source data is given. The levels have been checked using energy levels derived from sophisticated variational calculations. These levels span 107 vibrational states including members of all polyads up to and including 8v. Band origins, in some cases estimates, are presented for 101 vibrational modes.
250 citations
TL;DR: In this paper, the potential energy and dipole moment hypersurfaces for the isomerising HCN-HNC system are computed, using a grid of 242 points, principally at the all-electron cc-pCVQZ CCSD(T) level.
Abstract: Ab initio semiglobal potential energy and dipole moment hypersurfaces for the isomerising HCN–HNC system are computed, using a grid of 242 points, principally at the all-electron cc-pCVQZ CCSD(T) level. Several potential energy hypersurfaces (PES) are presented including one which simultaneously fits 1527 points from earlier ab initio, smaller basis CCSD(T) calculations of Bowman et al. [J. Chem. Phys. 99, 308 (1993)]. The resulting potential is then morphed with 17 aug-cc-pCVQZ CCSD(T) points calculated at HNC geometries to improve the representation of the HNC part of the surface. The PES is further adjusted to coincide with three ab initio points calculated, at the cc-pCV5Z CCSD(T) level, at the critical points of the system. The final PES includes relativistic and adiabatic corrections. Vibrational band origins for HCN and HNC with energy up to 12 400 cm−1 above the HCN zero-point energy are calculated variationally with the new surfaces. Band transition dipoles for the fundamentals of HCN and HNC, and a few overtone and hot band transitions for HCN have been calculated with the new dipole surface, giving generally very good agreement with experiment. The rotational levels of ground and vibrationally excited states are reproduced to high accuracy.
101 citations
TL;DR: New laboratory measurements are presented for the near-infrared and visible spectrum (8600-15 000 cm(-1)) of water vapor, expected to substantially increase the calculated absorption of solar energy due to water vapor in climate models.
90 citations
TL;DR: In this article, a simple approach for approximating Lamb shifts, the leading quantum electrodynamical (QED) effects, in molecules containing light elements, was presented, and the Lamb-shift contributions to the electronic energies were estimated from scaled nuclear and electronic Darwin terms.
Abstract: A simple approach is presented for approximating Lamb shifts, the leading quantum electrodynamical (QED) effects, in molecules containing light elements. The Lamb-shift contributions to the electronic energies are estimated from scaled nuclear and electronic Darwin terms. QED effects on the rovibrational states of water are found to be significantly larger than current experimental uncertainties, and only one order of magnitude smaller than current computational uncertainties.
83 citations
TL;DR: In this paper, the rotational excitation rates for electron collisions with linear molecular ions were investigated and the widely used Coulomb-Born approximation was shown to be valid for Δj = 1 transitions when the molecular ion has a dipole greater than about 2D.
Abstract: Molecular R-matrix calculations are performed to give rotational excitation rates for electron collisions with linear molecular ions. Results are presented for CO+, HCO+, NO+ and H2+ up to electron temperatures of 10 000 K. De-excitation rates and critical electron densities are also given. It is shown that the widely used Coulomb-Born approximation is valid for Δj=1 transitions when the molecular ion has a dipole greater than about 2D, but otherwise is not reliable for studying electron-impact rotational excitation. In particular, transitions with Δj>1 are found to have appreciable rates and are found to be entirely dominated by short-range effects.
80 citations
TL;DR: The new laboratory measurements of R. Schermaul et al. are combined with accurate calculations of weaker lines to provide a new, comprehensive linelist of water transitions for the spectral region 8600-15 000 cm(-1), reproduces the raw laboratory observations to a high level of agreement at all but the longest wavelengths.
76 citations
01 Jan 2001
TL;DR: All knowledge about molecules outside of the authors' solar system comes from study of their spectra, and laboratory measurements are usually the prime source for the data needed to interpret astronomical observations.
Abstract: All knowledge about molecules outside of our solar system comes from study of their spectra. Although laboratory measurements are usually the prime source for the data needed to interpret astronomical observations, there are a number of reasons why theory has played, and will continue to play, a central role in the study of molecules in space.
56 citations
TL;DR: Two-electron relativistic corrections to the ground-state electronic energy of water are determined as a function of geometry at over 300 points in this paper, which are used to calculate vibrational band origins and rotational term values.
39 citations
TL;DR: In this paper, potential energy hypersurfaces (PES) have been constructed for the ground electronic state of H2S utilizing results from state-of-the-art ab initio quantum chemical methods, most notably higher-order coupled cluster theory employing correlation-consistent basis sets.
Abstract: Potential energy hypersurfaces (PES) have been constructed for the ground electronic state of H2S utilizing results from state-of-the-art ab initio quantum chemical methods, most notably higher-order coupled cluster theory employing (core-polarized) correlation-consistent basis sets. Small corrections due to extrapolation to the complete basis set and full configuration interaction limits, core correlation, and relativistic corrections, as well as effects beyond the Born–Oppenheimer approximation have been investigated and incorporated into the final PES. Using the exact rovibrational kinetic energy operator rovibrational energy levels have been computed with the different PESs. The final converged ab initio PES of this study reproduces the available vibrational band origins of H2 32S, HD32S, D2 32S, and H2 34S with maximum deviations, gradually increasing for increased vibrational excitation, of 29(14 300), 10(3800), 7(4600), and 12(6400) cm−1, respectively, where the maximum energy above the zero-point ...
39 citations
TL;DR: The method of pulsed cavity-ring-down spectroscopy was employed to record the water vapor absorption spectrum, which consists of 1830 lines, calibrated against the iodine standard, which are not obtained in the HITRAN 96 database, while 243 are not included in the newly recorded Fourier transform spectrum of the Reims group.
29 citations
TL;DR: In this paper, the major pathway for the electron impact dissociation of H2 is through excitation to b 3 + + +, and the formal expressions needed for such calculations, which involve three fragments in the exit channel, are derived.
Abstract: At low energies, the major pathway for the electron impact dissociation of H2 is through excitation to b 3 � + . Ab initio calculations using the adiabatic nuclei, energy balance model of Stibbe and Tennyson (1998 New J. Phys. 1 2.1) of total cross sections, angular differential cross sections, energy differential cross sections and double differential cross sections for the electronic ground state initial vibrational v = 0 level, dissociating into continuum states are presented. The formal expressions needed for such calculations, which involve three fragments in the exit channel, are derived.
TL;DR: In this paper, the GENLN2 line-by-line code was used to assess the effects of such changes in the water vapour spectral database on calculations of clear-sky short-wave fluxes and heating rates.
Abstract: I New laboratory measurements and theoretical calculations of integrated line intensities for water vapour bands in the near-infrared and visible regions (8600-15 000 cm -1 ) show a systematic 6-26% increase in band intensities compared to the HITRAN96 database. We have used the GENLN2 line-by-line code to assess the effects of such changes in the water vapour spectral database on calculations of clear-sky short-wave fluxes and heating rates. Three standard atmospheres were used and it was found that, compared with HITRAN96 results, the absorbed downward solar fluxes increase (including the effects of theoretically predicted weak water lines in the region) by 5.5, 4.8 and 2.2 W m -2 (solar zenith angle = 30°) and by 2.4, 2.1 and 1.1 W m -2 (solar zenith angle = 75°) respectively. The maximum change in heating rate is about 4%. The effects are about five to eight times larger than those produced by using the Giver et al. corrections. The combined effects of the revised description of the spectroscopy of water vapour account for approximately 30-90% of the absorption currently ascribed to the water vapour continuum in this spectral region.
TL;DR: In this article, a Fourier transform spectrum has been recorded of a H2O/D2O vapor mixture in the wavenumber range 16,300 to 22,800 cm(-1) using a long path cell.
TL;DR: In this article, the R-matrix method is used to calculate elastic and excitation cross sections of four low-lying electronic states of the OClO molecule, designated as the X 2B1, 1 2A1 and 1 2B2 states.
Abstract: The R-matrix method is used to calculate elastic and excitation cross sections of four low-lying electronic states of the OClO molecule, designated as the X 2B1, 1 2A1, 1 2B2 and 1 2A2 states. Eight states, four doublets and four quartets are included in the close-coupled expansion; these excited states are predicted to have vertical excitation energies in the range 2.956-8.206 eV, in fair agreement with published multireference configuration-interaction calculations. The experimentally determined excitation energy of the atmospherically most important state 1 2A2 centred around 3.5 eV is in excellent agreement with our value of 3.44 eV. A bound state of OClO- with 1A1 symmetry with an adiabatic electron affinity of 1.558 eV at equilibrium geometry of OClO is found. There is a shape resonance of 3B1 symmetry at 2.96 eV and higher-lying shape resonances of 1B1, 1A2 and 3A2 symmetries located at 5.75, 8.06 and 7.22 eV, respectively. All the resonances are rather broad. The resonance positions correlate well with the maxima found in dissociative electron attachment cross section measurements. Rotationally inelastic scattering cross sections are compared with experiment and there is very good agreement for electron energies above 100 meV. Excitation cross sections for three excited states are presented for electron-impact energies up to 10 eV. Total integral cross sections are also compared with experiment.
TL;DR: In this paper, the elastic and excitation cross sections of seven low-lying electronically excited states of the Cl2O molecule were calculated using the R-matrix method, and an electronically bound, but probably dissociative, state was found with 2A1 symmetry with an adiabatic electron affinity of 0.4423 eV at the equilibrium geometry of Cl 2O.
Abstract: The R-matrix method is used to calculate the elastic and excitation cross sections of seven low-lying electronically excited states of the Cl2O molecule. Sixteen states consisting of eight singlets and eight triplets are included in the close-coupled expansion. These states have vertical excitation energies in the range 3.17-8.75 eV, which are in fair agreement with other more sophisticated calculations. We find an electronically bound, but probably dissociative, state of Cl2O- with 2A1 symmetry with an adiabatic electron affinity of 0.4423 eV at the equilibrium geometry of Cl2O. There is a shape dissociative resonance of 2B2 symmetry at 2.096 eV. We also find core-excited shape resonances in 2A1, 2A2, 2B1 and 2B2 symmetries. Cross sections are obtained for rotationally elastic and electronically inelastic scattering for electron impact energies up to 10 eV. Anionic and neutral dissociation products are considered.
TL;DR: In this article, Fourier transform emission spectra were recorded using a mixture of H2O and D2O at a temperature of 1500 degreesC at three overlapping sections and cover the wavenumber range 380-2190 cm(-1).
Journal Article•
TL;DR: Schermaul et al. as mentioned in this paper combined laboratory measurements of R. Schermaul er al. (J. Mel. Spectrosc. 208), for the near-infrared and visible spectrum of water vapor, covering the 2 nu + delta, 3 nu, 3nu+ delta, and 4 nu polyads, with accurate calculations of weaker lints to provide a new, comprehensive linelist of water transitions for the spectral region 8600-15 000 cm(-1).
TL;DR: In this paper, the role of H3+ has been explored in determining the atmospheric structure of both the gas giants and cool metal-free planets, as well as the prospects for future observations.
01 Jan 2001
TL;DR: In this article, a line-by-line code is used to assess the effects of such changes in the water vapour spectral database on calculations of short-wave fluxes and heating rates for three standard atmospheres.
Abstract: New laboratory measurements and theoretical calculations of integrated line intensities for water vapour bands in the near-infrared and visible regions (860015000 cm(-1)) show a systematic 6 to 26% increase in band intensities compared to the HITRAN96 database. The recent corrections to HITRAN96 (Giver et al, 2000) do not remove these discrepancies - in fact increasing them to 6 to 38%. A line-by-line code is used to assess the effects of such changes in the water vapour spectral database on calculations of short-wave fluxes and heating rates for three standard atmospheres. It is found that, compared with HT96 results, the absorbed downward solar fluxes increase by 4.8, 5.5 and 2.2 Wm(-1) (solar zenith angle = 30degrees) and by 2.1, 2.4 and 1.1 Wm(-2) (solar zenith angle = 75degrees) for mid-latitude summer, tropical and sub-arctic winter atmospheres respectively. The maximum percentage change in heating rate is about 4%.