N(4S), N(2D), and N(2P) yields in predissociation of excited singlet states of N2

Walter, C. W.; Cosby, P. C.; Helm, H.

doi:10.1063/1.466152

Cited by 70 publications

(76 citation statements)

References 22 publications

(5 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1, these mechanisms result in primarily N( 4 S )+N( 2 D) dissociation products, i.e., one of the nitrogen atoms is formed in an excited electronic state which decays on a timescale of 17 h into the ground state N( 4 S ). This is consistent with the observations of Walter et al (1993) who failed to detect direct N( 4 S )+N( 4 S ) dissociation products.…”

Section: Photoabsorption and Photodissociation Spectrumsupporting

confidence: 82%

Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

138

View full text Add to dashboard Cite

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.

show abstract

Section: Photoabsorption and Photodissociation Spectrumsupporting

confidence: 82%

Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

138

View full text Add to dashboard Cite

show abstract

“…[24][25][26] The excitation of predissociative states from charge-exchanged molecular beams has also provided information about the excitation levels of atomic photofragments. 27,28 Much less is known about the less abundant N 2 isotopomers. There have been several studies over the years of isotopically purified samples of 15 N 2 (Refs.…”

Section: Introductionmentioning

confidence: 99%

High-resolution Fourier-transform extreme ultraviolet photoabsorption spectroscopy of 14N15N

Heays¹,

Dickenson²,

Salumbides³

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

The first comprehensive high-resolution photoabsorption spectrum of 14 N 15 N has been recorded using the Fourier-transform spectrometer attached to the Desirs beamline at the Soleil synchrotron. Observations are made in the extreme ultraviolet and span 100 000-109 000 cm −1 (100-91.7 nm). The observed absorption lines have been assigned to 25 bands and reduced to a set of transition energies, f values, and linewidths. This analysis has verified the predictions of a theoretical model of N 2 that simulates its photoabsorption and photodissociation cross section by solution of an isotopomer independent formulation of the coupled-channel Schrödinger equation. The mass dependence of predissociation linewidths and oscillator strengths is clearly evident and many local perturbations of transition energies, strengths, and widths within individual rotational series have been observed.

show abstract

“…The branching ratio measurements for the N 2 predissociation were first made by Helm and Cosby 13,14 in their fast molecular beam setup. The N 2 molecules were prepared in a metastable state, which is very similar to the ground state a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Communication: Branching ratio measurements in the predissociation of 12C16O by time-slice velocity-map ion imaging in the vacuum ultraviolet region

Gao

Song

Yang

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

The first direct branching ratio measurement of the three lowest energy dissociation channels of CO that produce C( 3 P) + O( 3 P), C( 1 D) + O( 3 P), and C( 3 P) + O( 1 D) is reported. Rotational resolved carbon ion yield spectra for two bands (W(3sσ ) 1 (v = 3) at 108 012.6 cm −1 and 1 (v = 2) at 109 017 cm −1 ) and two bands ((4sσ ) 1 + (v = 4) at 109 452 cm −1 and (4pσ ) 1 + (v = 3) at 109 485 cm −1 ) of CO were obtained. Our measurements show that the branching ratio in this energy region is strongly dependent on the electronic and vibrational energy but it is independent or just weakly dependent on the parity and rotational energy levels. To our knowledge, this is the first time that the triplet channel producing O( 1 D) has been experimentally observed and this is also the first time that a direct measurement of the branching ratio for the different channels in the predissociation of CO in this energy region has been made.

show abstract

N(4S), N(2D), and N(2P) yields in predissociation of excited singlet states of N2

Cited by 70 publications

References 22 publications

Photodissociation of interstellar N₂

Photodissociation of interstellar N₂

High-resolution Fourier-transform extreme ultraviolet photoabsorption spectroscopy of 14N15N

Communication: Branching ratio measurements in the predissociation of 12C16O by time-slice velocity-map ion imaging in the vacuum ultraviolet region

Contact Info

Product

Resources

About

N(4S), N(2D), and N(2P) yields in predissociation of excited singlet states of N2

Cited by 70 publications

References 22 publications

Photodissociation of interstellar N2

Photodissociation of interstellar N2

High-resolution Fourier-transform extreme ultraviolet photoabsorption spectroscopy of 14N15N

Communication: Branching ratio measurements in the predissociation of 12C16O by time-slice velocity-map ion imaging in the vacuum ultraviolet region

Contact Info

Product

Resources

About

Photodissociation of interstellar N₂

Photodissociation of interstellar N₂