Experimental and theoretical studies of excited states of H2 observed in the absorption spectrum: I. The 5pπD″ 1Πu state

Glass‐Maujean, M.; Jungen, Ch.; Spielfiedel, A.; Schmoranzer, H.; Tulin, I.; Knie, André; Reiß, Philipp; Ehresmann, A.

doi:10.1016/j.jms.2013.09.010

Cited by 20 publications

(23 citation statements)

References 49 publications

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“…In this case, care needs to be taken not to underestimate the integrated cross section, potentially by more than an order of magnitude (Hudson & Carter 1968). Due to this issue, for some molecules (e.g., H 2 , N 2 , and CO) the recorded absorption spectra must be analysed line-by-line and the true cross section reconstructed without the limitation of experimental broadening (Eidelsberg et al 1992;Heays et al 2011;Glass-Maujean et al 2013c).…”

Section: Experimental Cross Sectionsmentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

428

442

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A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H 2 O and NH 3 photodissociation forming OH, O, NH 2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

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Section: Experimental Cross Sectionsmentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

428

442

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“…Note the particular characteristic of the n = 5-7 np 1 Π u Rydberg states, which dissociate to a ground state atom and another with a principal quantum number H(n − 1), i.e., 5pπ → H(1s) + H(4f); 6pπ → H(1s) + H(5f); 7pπ → H(1s) + H(6d) [27][28][29]. The electron configuration changes as a function of the internuclear distance R, e.g., the low vibrational levels of the 5p 1 Π u follow a diabatic potential that extrapolates to the n = 5 limit, and not the n = 4 dissociation limit at R → ∞.…”

Section: Resonant Ionizationmentioning

confidence: 99%

“…Recent analysis of one-photon absorption measurements using XUV synchrotron radiation in the range of 74-81 nm demonstrated that autoionization completely dominates over the other two competing channels in the case of n > 5 [31]. Using the n = 5-7 level energies of the Rydberg levels reported in [27][28][29], the detection laser was scanned in the vicinity of the expected transition energies, where it turned out that transitions to 7pπ, v = 5, resulted in sufficient H + 2 signal enhancement. The maximum FCF overlap for the D 1 Π u −F 1 Σ + g system is 0.34 for the (8, 0) band, while the corresponding D−F (5, 0) band only has an FCF of 0.022 [26].…”

Section: Resonant Ionizationmentioning

confidence: 99%

Precision measurements and test of molecular theory in highly excited vibrational states of H2 (v = 11)

et al. 2016

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Accurate EF 1 Σ + g − X 1 Σ + g transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, v = 11, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H * 2 , produced via the photodissociation of H 2 S, yielding transition frequencies with accuracies of 45 MHz or 0.0015 cm −1 . An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing 7pπ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known EF level energies, the level energies of X(v = 11, J = 1, 3 − 5) states are derived with accuracies of typically 0.002 cm −1 . These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.

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“…Local perturbations of this type occur recurrently in the spectrum of diatomic hydrogen, e.g. in the 5pπ state of H 2 where several such situations have been identified [14]. The v = 13, N = 3 value is new.…”

Section: The 4pπd Statementioning

confidence: 96%

Experimental and theoretical study of the npπ1Πu- (
Glass‐Maujean
¹
,
Vasserot
²
,
Jungen
³

et al. 2015
Journal of Molecular Spectroscopy
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The absolute absorption cross section and the branching ratios for the competing decay channels fluorescence, dissociation, and ionization of photoexcited long-lived 1 Π − u superexcited molecular levels in 2 Highlights • 319 photoabsorption transitions to npπ 1 Π − u upper levels of D 2 measured and assigned • 141 previously unknown spectral lines observed and assigned • Absolute absorption spectral line intensities measured • Dissociation, ionization and fluorescence branching ratios measured • Calculation from first principles of perturbed intensities and transitions

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Experimental and theoretical studies of excited states of H2 observed in the absorption spectrum: I. The 5pπD″ 1Πu state

Cited by 20 publications

References 49 publications

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Precision measurements and test of molecular theory in highly excited vibrational states of H2 (v = 11)

Experimental and theoretical study of the npπ1Πu- (
Glass‐Maujean
¹
,
Vasserot
²
,
Jungen
³

et al. 2015
Journal of Molecular Spectroscopy
Self Cite

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Experimental and theoretical studies of excited states of H2 observed in the absorption spectrum: I. The 5pπD″ 1Πu state

Cited by 20 publications

References 49 publications

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Precision measurements and test of molecular theory in highly excited vibrational states of H2 (v = 11)

Experimental and theoretical study of the npπ1Πu- (Glass‐Maujean1, Vasserot2, Jungen3 et al. 2015Journal of Molecular SpectroscopySelf Cite

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Experimental and theoretical study of the npπ1Πu- (
Glass‐Maujean
¹
,
Vasserot
²
,
Jungen
³

et al. 2015
Journal of Molecular Spectroscopy
Self Cite