High resolution studies of dipole-forbidden states of N<sub>2</sub>using low-energy electron energy-loss spectroscopy

Wilden, D G; Hicks, Peter; Comer, John

doi:10.1088/0022-3700/12/9/010

Cited by 26 publications

(7 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In Figure 4, we present an enlarged view of the q-dependence of this spectral region in the EELS and NIXS results. These data immediately motivate our central observation: both the line-shape and the central energy of this feature evolve strongly with increasing q. Surveying prior work at sufficiently high q, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]64] this has not previously been noted; in fact, very few presentations of raw spectra (as opposed to integrated GOS(q) summaries) appear in the literature. Complications in the qdependence of the vibrational structure (e.g.…”

Section: Resultssupporting

confidence: 60%

“…In particular, we use the measurements (by both EELS and NIXS) from Bradley et al [1] together with new TDDFT calculations, all presented in absolute units, to quantitatively investigate the Lyman-Birge-Hopfield (LBH) resonance band of N 2 as a function of momentum transfer. The LBH band includes the three lowest energy singlet electronic excitations of N 2 and has seen decades of study [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. The properties of the LBH band have been pursued both for fundamental reasons and also because of its importance for atmospheric electricity and optical emission for the Earth and the moons Titan and Triton [31,[47][48][49].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reexamining the Lyman-Birge-Hopfield band of N2

et al. 2011

View full text Add to dashboard Cite

Motivated by fundamental molecular physics and by atmospheric and planetary sciences, the valence excitations of N 2 gas have seen several decades of intensive study, especially by electron energy loss spectroscopy (EELS). It was consequently surprising when a comparison of nonresonant inelastic x-ray scattering (NIXS) and nonresonant EELS found strong evidence for violations of the first Born approximation for EELS when leaving the dipole scattering limit. Here we reassess the relative strengths of the constituent resonances of the lowest energy excitations of N 2 , encompassed by the socalled Lyman-Birge-Hopfield (LBH) band, by expanding on the prior, qualitative, interpretation of the NIXS results for N 2 by both quantifying the GOS of the lowestenergy excitations and also presenting a new time-dependent density functional theory calculation of the q-dependence of the entire low-energy electronic excitation spectrum.At high q, we find that the LBH band has an unexpectedly large contribution from the octupolar w 1 Δ u resonance exactly in the regime where theory and EELS experiment for the presumed-dominant a 1 Π g resonance have previously had substantial disagreement, and also where the EELS results must now be expected to show violations of the first Born approximation. After correcting for this contamination, the a 1 Π g GOS from the NIXS results is in good agreement with prior theory. The NIXS spectra, over their entire q range, also find satisfactory agreement with the new TDDFT calculations for both bound and continuum excitations.

show abstract

Section: Resultssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Reexamining the Lyman-Birge-Hopfield band of N2

et al. 2011

View full text Add to dashboard Cite

show abstract

“…We calculate vertical excitation energies and oscillator strengths of five small molecules, N 2 , CO, H 2 CO, C 2 H 4 , and C 6 H 6 , which have already been extensively studied theoretically [13,27,[56][57][58][59] and experimentally [60][61][62][63]. In order to have unique, comparable references, equationof-motion coupled-cluster singles doubles (EOM-CCSD) calculations were done in the same basis with the quantum chemistry program Gaussian 09 [64].…”

Section: Computational Detailsmentioning

confidence: 99%

Electronic excitations from a linear-response range-separated hybrid scheme

2013

View full text Add to dashboard Cite

We study linear-response time-dependent density-functional theory (DFT) based on the singledeterminant range-separated hybrid (RSH) scheme, i.e. combining a long-range Hartree-Fock exchange kernel with a short-range DFT exchange-correlation kernel, for calculating electronic excitation energies of molecular systems. It is an alternative to the more common long-range correction (LC) scheme which combines a long-range Hartree-Fock exchange kernel with a short-range DFT exchange kernel and a standard full-range DFT correlation kernel. We discuss the local-density approximation (LDA) to the short-range exchange and correlation kernels, and assess the performance of the linear-response RSH scheme for singlet → singlet and singlet → triplet valence and Rydberg excitations in the N2, CO, H2CO, C2H4, and C6H6 molecules, and for the first charge-transfer excitation in the C2H4-C2F4 dimer. For these systems, the presence of long-range LDA correlation in the ground-state calculation and in the linear-response kernel has only a small impact on the excitation energies and oscillator strengths, so that the RSH method gives results very similar to the ones given by the LC scheme. Like in the LC scheme, the introduction of long-range HF exchange in the present method corrects the underestimation of charge-transfer and high-lying Rydberg excitation energies obtained with standard (semi)local density-functional approximations, but also leads to underestimated excitation energies to low-lying spin-triplet valence states. This latter problem is largely cured by the Tamm-Dancoff approximation which leads to a relatively uniform accuracy for all excitation energies. This work thus suggests that the present linear-response RSH scheme is a reasonable starting approximation for describing electronic excitation energies, even before adding an explicit treatment of long-range correlation.

show abstract

“…Ethylene has been studied exhaustively in the vapor and crystalline phases; earlier results have been summarized by Robin [3]. Electron energy loss spectroscopy (EELS) revealed that the 1 vertical transition occurs at 97 kcal/mol [4,5]. Electron impact spectroscopy (EIS) has established the singlet-triplet vertical excitation energy to lie in the range 97-108 kcal/mol [6].…”

Section: Introductionmentioning

confidence: 99%

Quantum Monte Carlo study of singlet–triplet transition in ethylene

Akramine

Kollias

Lester

2003

The Journal of Chemical Physics

View full text Add to dashboard Cite

A theoretical study is reported of the transition between the ground state ( and the lowest triplet state( ) of ethylene based on the diffusion Monte Carlo (DMC) variant of the quantum Monte Carlo method. Using DMC trial functions constructed from Hartree-Fock, complete active space self-consistent field and multi-configuration self-consistent field wave functions, we have computed the atomization energy and the heat of formation of both states, and adiabatic and vertical energy differences between these states using both all-electron and effective core potential DMC. The ground state atomization energy and heat of formation are found to agree with experiment to within the error bounds of the computation and experiment.Predictions by DMC of the triplet state atomization energy and heat of formation are presented.The adiabatic singlet-triplet energy difference is found to differ by 5 kcal/mol from the value obtained in a recent photodissociation experiment.1

show abstract

High resolution studies of dipole-forbidden states of N₂using low-energy electron energy-loss spectroscopy

Cited by 26 publications

References 31 publications

Reexamining the Lyman-Birge-Hopfield band of N2

Reexamining the Lyman-Birge-Hopfield band of N2

Electronic excitations from a linear-response range-separated hybrid scheme

Quantum Monte Carlo study of singlet–triplet transition in ethylene

Contact Info

Product

Resources

About

High resolution studies of dipole-forbidden states of N2using low-energy electron energy-loss spectroscopy

Cited by 26 publications

References 31 publications

Reexamining the Lyman-Birge-Hopfield band of N2

Reexamining the Lyman-Birge-Hopfield band of N2

Electronic excitations from a linear-response range-separated hybrid scheme

Quantum Monte Carlo study of singlet–triplet transition in ethylene

Contact Info

Product

Resources

About

High resolution studies of dipole-forbidden states of N₂using low-energy electron energy-loss spectroscopy