Sign reversal of the spin-orbit constant for the C Π3u state of N2

Ndome, H.; Hochlaf, M.; Lewis, B. R.; Heays, A. N.; Gibson, S. T.; Lefebvre‐Brion, H.

doi:10.1063/1.2990658

Cited by 43 publications

(42 citation statements)

References 22 publications

(12 reference statements)

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“…It possesses a potential well of ~8700 cm -1 . Its electronic wavefunction is mainly described by the (2σ g ) 2 (3σ g ) 2 (1π u ) 2 (2σ u ) 2 (1π g ) 2 [31]. These authors calculated the potential curve for the 1 1 Γ g state up to R=3.2 bohr (= 1.693 Å) and found in their best SD calculation a pronounced minimum at 13.14 eV (= 106000 cm -1 ).…”

Section: Potential Energy Curves and Spectroscopymentioning

confidence: 99%

“…Their spectroscopy, their dynamics, their mutual interaction and their perturbation by the close lying electronic states of N 2 are nicely discussed and reviewed in Refs. [1][2][3][4][5]. Briefly, these electronic states are accessible (favorable Franck-Condon factors) by optical transitions from the ground state (GS) of N 2 either by spin-allowed (singlet-singlet) or spin-forbidden (singlet-triplet) absorptions [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Hochlaf

Ndome

Hammoutène

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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Using an ab initio methodology, we compute the potential energy curves and the spinorbit coupling integrals of the N 2 electronic states located in the 0-120000 cm -1 energy domaine.In our analysis, we focus mostly on those located outside the Franck-Condon regio n accessible from the ground state of N 2 i.e. the two strongly bound states 1 3 Σ g -and 1 1 Γ g , and the weakly bound state 2 3 Σ g -, in addition to several repulsive states. We characterize them spectroscopically and we compute their spin-orbit couplings to the close lying singlets, triplets and quintets. This work completes our knowledge on the electronic states of N 2 that may be important intermediates during N + N collisions and for the dynamics of the N 2 singlets and triplets and quintets VUV photodissociation.

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Section: Potential Energy Curves and Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Hochlaf

Ndome

Hammoutène

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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“…Moreover, these lines can be shielded by lines of more abundant species such as H, H 2 and CO. Until recently, accurate N 2 molecular data to simulate these processes were not available. Thanks to a concerted laboratory (e.g., Ajello et al 1989;Helm et al 1993;Sprengers et al 2003Sprengers et al , 2004Sprengers et al , 2005Stark et al 2008;Lewis et al 2008b;Heays et al 2009 and theoretical (e.g., Spelsberg & Meyer 2001;Lewis et al 2005aLewis et al ,b, 2008cHaverd et al 2005;Ndome et al 2008) effort over the past two decades, this information is now available.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

Self Cite

138

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Context. Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks, but its photodissociation under interstellar conditions has never been properly studied. The partitioning of nitrogen between N and N 2 controls the formation of more complex prebiotic nitrogen-containing species. Aims. The aim of this work is to gain a better understanding of the interstellar N 2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. Methods. We used an approach similar to that adopted for CO in which we simulated the full high-resolution line-by-line absorption + dissociation spectrum of N 2 over the relevant 912-1000 Å wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schrödinger equation. The simulated N 2 spectra were compared with the absorption spectra of H 2 , H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a protoplanetary disk. Results. The unattenuated photodissociation rate in the Draine (1978, ApJS, 36, 595) radiation field assuming an N 2 excitation temperature of 50 K is 1.65 × 10 −10 s −1 , with an uncertainty of only 10%. Most of the photodissociation occurs through bands in the 957-980 Å range. The N 2 rate depends slightly on the temperature through the variation of predissociation probabilities with rotational quantum number for some bands. Shielding functions are provided for a range of H 2 and H column densities, with H 2 being much more effective than H in reducing the N 2 rate inside a cloud. Shielding by CO is not effective. The new rates are 28% lower than the previously recommended values. Nevertheless, diffuse cloud models still fail to reproduce the possible detection of interstellar N 2 except for unusually high densities and/or low incident UV radiation fields. The transition of N → N 2 occurs at nearly the same depth into a cloud as that of C + → C → CO. The orders-of-magnitude lower N 2 photodissociation rates in clouds exposed to black-body radiation fields of only 4000 K can qualitatively explain the lack of active nitrogen chemistry observed in the inner disks around cool stars. Conclusions. Accurate photodissociation rates for N 2 as a function of depth into a cloud are now available that can be applied to a wide variety of astrophysical environments.

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“…This work considered in detail the sharply structured absorption spectrum of N 2 and shielding species. This was made possible by means of an accurate and comprehensive quantum-mechanical model of N 2 photoabsorption and dissociation, which was informed by an extensive history of N 2 spectroscopy in the laboratory (e.g., Ajello et al 1989;Helm et al 1993;Sprengers et al 2003Sprengers et al , 2004Sprengers et al , 2005aStark et al 2008;Lewis et al 2008b;Heays et al 2009 and theoretically (e.g., Spelsberg & Meyer 2001;Lewis et al 2005bLewis et al ,a, 2008aHaverd et al 2005;Ndome et al 2008). This model, detailed in Sect.…”

Section: Introductionmentioning

confidence: 99%

Isotope selective photodissociation of N₂by the interstellar radiation field and cosmic rays

Heays

Visser

Gredel

et al. 2014

A&A

107

130

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Context. Photodissociation of 14 N 2 and 14 N 15 N occurs in interstellar clouds, circumstellar envelopes, protoplanetary discs, and other environments due to ultraviolet radiation originating from stellar sources and the presence of cosmic rays. This source of N atoms initiates the formation of more complex N-bearing species and may influence their isotopic composition. Aims. We study the photodissociation rates of 14 N 15 N by ultraviolet continuum radiation and both isotopologues in a field of cosmic ray induced photons. To determine the effect of these on the isotopic composition of more complex molecules. Methods. High-resolution theoretical photodissociation cross sections of N 2 are used from an accurate and comprehensive quantummechanical model of the molecule based on laboratory experiments. A similarly high-resolution spectrum of H 2 emission following interactions with cosmic rays has been constructed. The spectroscopic data are used to calculate photodissociation rates which are then input into isotopically differentiated chemical models, describing an interstellar cloud and a protoplanetary disc. N 2 , H 2 , and H are presented. Incorporating these into an interstellar cloud model, an enhancement of the atomic 15 N/ 14 N ratio over the elemental value is obtained due to the self-shielding of external radiation at an extinction of about 1.5 mag. This effect is larger where assumed grain growth has reduced the opacity of dust to ultraviolet radiation. The transfer of photolytic isotopic fractionation of N and N 2 to other molecules is demonstrated to be significant in a protoplanetary disc model with grain growth, and is species dependent with 15 N enhancement approaching a factor of 10 for HCN. The cosmic ray induced dissociation of CO is revisited employing a more recent photodissociation cross section, leading to a rate that is ∼40% lower than previously calculated.

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Sign reversal of the spin-orbit constant for the C Π3u state of N2

Cited by 43 publications

References 22 publications

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Photodissociation of interstellar N₂

Isotope selective photodissociation of N₂by the interstellar radiation field and cosmic rays

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Sign reversal of the spin-orbit constant for the C Π3u state of N2

Cited by 43 publications

References 22 publications

Valence–Rydberg electronic states of N2: spectroscopy and spin–orbit couplings

Valence–Rydberg electronic states of N2: spectroscopy and spin–orbit couplings

Photodissociation of interstellar N2

Isotope selective photodissociation of N2by the interstellar radiation field and cosmic rays

Contact Info

Product

Resources

About

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Valence–Rydberg electronic states of N₂: spectroscopy and spin–orbit couplings

Photodissociation of interstellar N₂

Isotope selective photodissociation of N₂by the interstellar radiation field and cosmic rays