Lifetime and predissociation yield of N214bΠu1(v=1) revisited: Effects of rotation

Lewis, B. R.; Gibson, S. T.; Sprengers, J. P.; Ubachs, Wim; Johansson, Ann; Wahlström, Claes‐Göran

doi:10.1063/1.2137722

Cited by 39 publications

(56 citation statements)

References 11 publications

(12 reference statements)

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“…For the 1 Π u states considered here, spinorbit coupling to the strongly-coupled and -predissociated 3 Π u manifold (red PECs in Fig. 1), with ultimate dissociation via the C state, provides the predissociation mechanism (Lewis et al 2005a(Lewis et al , 2008c, with a minor contribution from a crossing by the 2 3 Σ + u state (green PEC in Fig. 1) at higher energies.…”

Section: Photoabsorption and Photodissociation Spectrummentioning

confidence: 99%

“…The same cannot be said for the line-by-line models such as those employed for CO, which would also benefit from a CSE approach. The detailed CSE model for N 2 employed here has been described in 1 incorporates earlier models of the 1 Π u (Lewis et al 2005a;Haverd et al 2005) and 3 Π u states (Lewis et al 2008c) and has been tested extensively against laboratory data, including high-resolution spectra obtained at the SOLEIL synchrotron facility . A complete discussion of the CSE model and a full listing of computed spectroscopic data is deferred to Heays et al (in prep.).…”

Section: Photoabsorption and Photodissociation Spectrummentioning

confidence: 99%

“…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%

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Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

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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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Section: Photoabsorption and Photodissociation Spectrummentioning

confidence: 99%

Section: Photoabsorption and Photodissociation Spectrummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

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138

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“…The molecules with a shorter lifetime (τ) have greater predissociation width and higher predissociation probability (η pre ). 24,25 Therefore, photoabsorption cross section (σ abs ) and photodissociation cross section (σ dis ) are related by σ dis = η pre × σ abs . For a limited spectral zone (i.e., 95.8 to 96.0 nm, c ′ (ν ′ = 0) level), η pre is shown to be small, and thus the dissociation cross section is drastically different from FIG.…”

Section: Resultsmentioning

confidence: 99%

“…33 Rotational states play a significant role in the predissociation process. 25 Rotational state dependent predissociation yields for b 1 Π u (ν = 1) of 14 N 2 have been detected. 27 Heays et al, 18 recently computed the isotopologue ( 14 N 2 and 14 N 15 N) dependent predissociation fraction (η pre ) for the same state (b 1 Π u (ν = 1)) as a function of rotation level (J), which shows a strong J-dependency of the predissociation process.…”

Section: E Temperature Dependent Profilementioning

confidence: 99%

Nitrogen isotopic fractionations in the low temperature (80 K) vacuum ultraviolet photodissociation of N2

Chakraborty

Jackson

Rude

et al. 2016

The Journal of Chemical Physics

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N2 is a diatomic molecule with complex electronic structure. Interstate crossings are prominent in the high energy domain, introducing significant perturbations to the system. Nitrogen mainly photodissociates in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum through both direct and indirect predissociation. Due to the complexity introduced by these perturbations, the nitrogen isotopic fractionation in N2 photodissociation is extremely hard to calculate, and an experimental approach is required. Here we present new data of N-isotopic fractionation in N2 photodissociation at low temperature (80 K), which shows a distinctly different 15N enrichment profile compared to that at relatively higher temperatures (200 and 300 K). The new data, important to understanding the N-isotopic compositions measured in meteorites and other planetary bodies, are discussed in light of the knowledge of N2 photochemistry and calculated photoabsorption cross sections in the VUV.

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Precision Laser Spectroscopy in the Extreme Ultraviolet

Eikema

Ubachs

2011

Handbook of High‐resolution Spectroscopy

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Techniques for the production of short wavelengths in the extreme ultraviolet wavelength range are described, spanning low‐order harmonic generation in the perturbative regime for narrow bandwidth XUV production to the plateau‐regime with the three‐step collisional model for the generation of high harmonics with broadband ultrafast pulses. In addition, the intermediate regime is discussed for pulses of 300 ps duration, as well as the regime of harmonic conversion based on continuous wave lasers aiming at the production of coherent Lyman‐α radiation. Applications of XUV sources in the frequency domain typically rely on the production of XUV‐light from narrowband Fourier‐transform‐limited pulses for recording high‐resolution spectra. Alternatively, harmonically upconverted pulses of ultrashort duration (with inter‐pulse coherence) can be used for spectroscopic studies in the time and frequency domain (such as direct frequency comb spectroscopy techniques). Examples of both approaches for atomic and molecular spectroscopy are discussed at some length. For precision metrology on atomic systems, a focus is put on the Lamb shift determination in the He ground state. In the realm of molecular spectroscopy, predissociation phenomena in the nitrogen molecule are highlighted, with relevance for dissociation processes occurring in the upper layers of the Earth atmosphere. Similar predissociation phenomena in carbon monoxide are also treated in some detail, in this case with relevance for the chemistry in interstellar clouds. Precision XUV spectroscopy of molecular hydrogen is discussed as well, as it relates to the possibility of detecting a variation of the proton–electron mass ratio on a cosmological time scale. In the last section, applications of direct frequency comb spectroscopic techniques at short wavelengths are explained and prospects are given for using these techniques at extreme ultraviolet wavelengths.

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Lifetime and predissociation yield of N214bΠu1(v=1) revisited: Effects of rotation

Abstract: Lifetime and predissociation yield of N-14(2) b (1)Pi(u)(v=1) revisited: Effects of rotationLewis,

Cited by 39 publications

References 11 publications

Photodissociation of interstellar N₂

Photodissociation of interstellar N₂

Nitrogen isotopic fractionations in the low temperature (80 K) vacuum ultraviolet photodissociation of N2

Precision Laser Spectroscopy in the Extreme Ultraviolet

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Lifetime and predissociation yield of N214bΠu1(v=1) revisited: Effects of rotation

Abstract: Lifetime and predissociation yield of N-14(2) b (1)Pi(u)(v=1) revisited: Effects of rotationLewis,

Cited by 39 publications

References 11 publications

Photodissociation of interstellar N2

Photodissociation of interstellar N2

Nitrogen isotopic fractionations in the low temperature (80 K) vacuum ultraviolet photodissociation of N2

Precision Laser Spectroscopy in the Extreme Ultraviolet

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Product

Resources

About

Photodissociation of interstellar N₂

Photodissociation of interstellar N₂