The total excitation cross section of the c3Πustate of H2

Mason, Nigel J.; Newell, W R

doi:10.1088/0022-3700/19/17/008

Cited by 28 publications

(11 citation statements)

References 21 publications

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“…The ICS recomended by Yoon et al [1] follow the Wrkich et al [18] cross sections. We have also presented the relative excitation function measurements of [22] that were normalized at 20 eV to the ICS value of Khakoo and Trajmar [17] as given by Brunger and Buckman [3]. These data show a similar shape to the CCC cross sections but are about twice the magnitude in absolute values.…”

Section: B Excitation To Triplet Statesmentioning

confidence: 93%

“…These data show a similar shape to the CCC cross sections but are about twice the magnitude in absolute values. [17], Wrkich et al [18], and Mason and Newell [22], and calculations of Branchett et al [41] (RM), da Costa et al [42] (SMC), and Mu-Tao et al [39] (DW), and the recommended data of Yoon et al [1].…”

Section: B Excitation To Triplet Statesmentioning

confidence: 99%

“…For angle integrated cross sections (ICS) additional errors arise from an extrapolation procedure utilized by experiment to obtain DCS at angles inaccessible by the experiment. There are a large number of optical excitation function measurements [21][22][23][24][25][26][27]. Such measurements provide relative cross sections that are affected by largely unknown cascades.…”

Section: Introductionmentioning

confidence: 99%

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Electron-impact excitation of molecular hydrogen

2017

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Section: B Excitation To Triplet Statesmentioning

confidence: 93%

Section: B Excitation To Triplet Statesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron-impact excitation of molecular hydrogen

2017

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“…Khakoo et al (1987) and Khakoo & Segura (1994). Finally, the total excitation cross section for the c ¡ ¦ state was measured by Mason & Newell (1986).…”

Section: Experimental Workmentioning

confidence: 99%

Differential cross sections for near-threshold electron impact dissociation of molecular hydrogen

Trevisan

Tennyson

2001

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

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Electron impact dissociation of molecular hydrogen is considered to be a major route to molecular break-up in cool hydrogen plasmas. Such plasmas are found in a number of astrophysical environments and in the divertor region of tokamak fusion plasma.At low energies, the major pathway for the electron impact dissociation of H is throughdissociative excited electronic state. The purpose of this work is to develop a theoretical formulation for this process for an arbitrary diatomic molecule, and to derive the formal expressions that describe the differential and total cross sections, which involve three fragments in the exit channel, and to study the electron impact dissociation of molecular hydrogen and its isotopomers at near-threshold energies.Ab initio calculations of total cross sections, angular differential cross sections, energy differential cross sections and double differential cross sections are made for the § © vibrational level of H . The effect of nuclear motion is then included in such calculations, with the dissociation taking place from the electronic ground state at different initial vibrational levels, dissociating into continuum states.Studies of mixed isotopes are performed using the R-matrix method, and total cross sections, energy differential cross sections and rate coefficients for electron impact dissociation of H , D , T , HD, HT and DT as a function of the vibrational states are presented.Finally, a scaling rule that describes integral cross sections as a function of the initial vibrational state, the reduced mass of the target molecule and the energy of the projectile electron is developed and compared against cross sections calculated accurately for the H molecule and its isotopomers.2

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“…From left to right and from top to bottom: momentum transfer cross section ("m.t.") -solid thick blue line(Pinto & Galli 2008, PG08), circles(Shyn & Sharp 1981, SS81), leftpointing triangles(Nishimura et al 1985, N85), squares(Khakoo & Trajmar 1986, KT86), right-pointing triangles(England et al 1988, E88), hexagons(Brunger et al 1990(Brunger et al , 1991, up-pointing triangles(Schmidt et al 1994, S94); rotational transition J = 0 → 2 -solid thick green line (present MCCC calculations), circles(England et al 1988, E88); vibrational transition v = 0 → 1 -solid thick red line(Yoon et al 2008, Y08), left-pointing triangles(Ehrhardt et al 1968, E68), squares(Linder & Schmidt 1971, LS71), up-pointing triangles(Nishimura et al 1985, N85), circles(Brunger et al 1991, B91); vibrational transition v = 0 → 2 -solid thick red line(Janev et al 2003, J03), circles(Ehrhardt et al 1968, E68);X 1 Σ + g → B 1 Σ + u and X 1 Σ + g → C 1 Π u singlettransitions -solid thick magenta line (Scarlett et al 2021a, MCCC), up-pointing triangles (Khakoo & Trajmar 1986, KT86), squares (Wrkich et al 2002, W02), left-pointing triangles (Kato et al 2008, K08), circles (Hargreaves et al 2017, H17); X 1 Σ + g → b 3 Σ + u triplet transition -dotted orange line (Yoon et al 2008, Y08), solid thick orange line (Scarlett et al 2021a, MCCC), up-pointing triangles(Hall & Andric 1984, HA84), circles(Nishimura & Danjo 1986, ND86), down-pointing triangles(Khakoo et al 1987, K87), squares(Khakoo & Segura 1994, KS94), right-pointing triangles (Zawadzki et al 2018a, Z18); X 1 Σ + g → c 3 Π u triplet transition -dotted orange line(Liu et al 2017, L17), solid thick orange line(Scarlett et al 2021a, MCCC), circles(Khakoo & Trajmar 1986, KT86), left-pointing triangles(Mason & Newell 1986, MN86), squares (Wrkich et al 2002, up-pointing triangles(Hargreaves et al 2017, H17); X 1 Σ + g → a 3 Σ + g triplet transition -solid thick orange line(Scarlett et al 2021a, MCCC), circles(Khakoo & Trajmar 1986, KT86), squares (Wrkich et al 2002, up-pointing triangles(Hargreaves et al 2017, H17).…”

mentioning

confidence: 99%

Cosmic rays in molecular clouds probed by H$_{2}$ rovibrational lines -- Perspectives for the James Webb Space Telescope

Padovani,

Bialy,

Galli

et al. 2022

Preprint

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Context. Low-energy cosmic rays (< TeV) play a fundamental role in the chemical and dynamical evolution of molecular clouds, as they control the ionisation, dissociation, and excitation of H 2 . Their characterisation is therefore important both for the interpretation of observations and for the development of theoretical models. However, the methods used so far for estimating the cosmic-ray ionisation rate in molecular clouds have several limitations due to uncertainties in the adopted chemical networks. Aims. We refine and extend the method proposed by Bialy (2020) to estimate the cosmic-ray ionisation rate in molecular clouds by observing rovibrational transitions of H 2 at near-infrared wavelengths, which are mainly excited by secondary cosmic-ray electrons. Methods. Combining models of interstellar cosmic-ray propagation and attenuation in molecular clouds with the rigorous calculation of the expected secondary electron spectrum and updated H 2 excitation cross sections by electron collisions, we derive the intensity of the four H 2 rovibrational transitions observable in dense, cold gas: (1 − 0)O(2), (1 − 0)Q(2), (1 − 0)S(0), and (1 − 0)O(4). Results. The proposed method allows the estimation of the cosmic-ray ionisation rate for a given observed line intensity and H 2 column density. We are also able to deduce the shape of the low-energy cosmic-ray proton spectrum impinging upon the molecular cloud. We also present a look-up plot and a web-based application that can be used to constrain the low-energy spectral slope of the interstellar cosmic-ray proton spectrum. We finally comment on the capability of the James Webb Space Telescope to detect these near-infrared H 2 lines, making it possible to derive for the first time spatial variation of the cosmic-ray ionisation rate in dense gas. Besides the implications for the interpretation of the chemical-dynamic evolution of a molecular cloud, it will finally be possible to test competing models of cosmic-ray propagation and attenuation in the interstellar medium, as well as compare cosmic-ray spectra in different Galactic regions.

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The total excitation cross section of the c³Π_ustate of H₂

Cited by 28 publications

References 21 publications

Electron-impact excitation of molecular hydrogen

Electron-impact excitation of molecular hydrogen

Differential cross sections for near-threshold electron impact dissociation of molecular hydrogen

Cosmic rays in molecular clouds probed by H$_{2}$ rovibrational lines -- Perspectives for the James Webb Space Telescope

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