Photofragment action spectroscopy of the acetylene molecule in the vacuum ultraviolet

Löffler, P.; Lacombe, D.; Ross, A.J.; Wrede, Eckart; Schnieder, L.; Welge, K. H.

doi:10.1016/0009-2614(96)00174-1

Cited by 30 publications

(58 citation statements)

References 33 publications

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“…A small isotopic shift following deuteration will lower the dissociation rate of C 2 HD in a Lyman-α dominated radiation field by a factor of 10. This reduction is in fact indicated from laboratory action spectroscopy of C 2 H 2 and C 2 HD (Löffler et al 1996;Wang et al 1997). …”

Section: Isotopic Effectsmentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

425

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: Isotopic Effectsmentioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

425

442

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“…In C 2 H 2 , the E valence state lifetime is significantly longer than the Rydberg state lifetime, confirming the results deduced from spectroscopy on H photofragments. 2,3,22 In the C 2 D 2 spectra the intensity distribution of the exciting pulse accounts for the intensities of the two features. An interesting result is the significant difference in the decay times observed in C 2 D 2 : the excitation of the cis mode seems to lead to a faster predissociation dynamics than the excitation of the trans mode.…”

Section: Results and Discussion Ofmentioning

confidence: 99%

“…The lifetimes of these states range from picoseconds to a few femtoseconds, even for states lying very close in energy. 2,3 In the present experiment, we apply a time-resolved spectroscopic technique capable of monitoring dynamics on a femtosecond time scale to Rydberg and valence states in C 2 H 2 and C 2 D 2 using an ultrashort pump pulse at about 9.4 eV. These states lie in the Rydberg (3d-4s) complex at about 2 eV below the ionization threshold.…”

Section: Introductionmentioning

confidence: 99%

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The predissociation of highly excited states in acetylene by time-resolved photoelectron spectroscopy

Zamith

Blanchet

Girard

et al. 2003

The Journal of Chemical Physics

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We study the dynamics of highly excited states in acetylene initiated by an ultrashort vacuum ultraviolet laser pulse. Electronic states lying in the 4s-3d Rydberg region are excited with one femtosecond pulse, and the dynamic development of the states is monitored by a second short pulse which ionizes the system. We show that even for femtosecond pulses where the bandwidth of the exciting pulse covers several electronic states, it is possible to extract short decay lifetimes through time-resolved photoelectron spectroscopy by using a frequency-modulated ͑chirped͒ excitation pulse. We report decay lifetimes for the F 4 0 2 and E 4-5 0 2 states in acetylene, and for the E 4 0 2 and E 5 0 2 states in d-acetylene. The time evolution measured in the electron spectra is compared to decay spectra measured using ion yield and the differences in these results are discussed.

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“…2, 8 Several experimental and theoretical investigations have been carried out to study the C 2 H radical reactivity, [9][10][11] its absorption spectroscopy, [12][13][14][15][16][17] and its production from acetylene photolysis. [18][19][20][21] Although a few theoretical works have been performed on the C 2 H + cation, [22][23][24][25] the experimental studies of this cation are scarcer. 12,26,27 Finally only three studies have measured indirectly the ionization energy (IE) of this important radical [28][29][30] and no experimental works have been published about its photoionizing transitions to our knowledge.…”

mentioning

confidence: 99%

Communication: On the first ionization threshold of the C2H radical

Gans

Garcia

Holzmeier

et al. 2017

The Journal of Chemical Physics

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The slow photoelectron spectrum of the ethynyl radical has been recorded for the first time by using the DESIRS beamline of the SOLEIL synchrotron facility. Ethynyl was generated using a microwave discharge flow tube. The observation of the X+Π3←XΣ+2 transition allowed the first direct measurement of the adiabatic ionization threshold of this radical (EI = 11.641(5) eV). The experimental results are supported by ab initio calculations. Our preliminary investigation of the cationic ground state potential energy surfaces predicts a non-negligible Renner-Teller effect which has not been discussed previously.

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Photofragment action spectroscopy of the acetylene molecule in the vacuum ultraviolet

Cited by 30 publications

References 33 publications

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

The predissociation of highly excited states in acetylene by time-resolved photoelectron spectroscopy

Communication: On the first ionization threshold of the C2H radical

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