Experimental evidence for the existence of a overbar(5,ϵ)f resonantly localised continuum state in uranium

Connerade, J P; Mansfield, M. W. D.; Cukier, Moisés; Pantelouris, M

doi:10.1088/0022-3700/13/7/003

Cited by 23 publications

(2 citation statements)

References 10 publications

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“…Also, high lying states of possible intermediate dissociative products, e.g., UF x or U may give rise to efficient ionization. In this connection, Connerade et al 45 have described a very high lying state at ::::; 100 eV in both UF 4 and atomic U.…”

Section: Discussionmentioning

confidence: 94%

Multiphoton ionization of uranium hexafluoride

Armstrong¹,

Harkins²,

Compton

et al. 1994

The Journal of Chemical Physics

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A novel, simple and efficient dye laser with low amplified spontaneous emission background for analytical fluorescence and ionization spectroscopy AIP Conf.Multiphoton ionization (MPI) time-of-flight mass spectroscopy (TOFMS) and photoelectron spectroscopy (PES) studies of UF 6 are reported using focused light from the Nd:YAG laser fundamental (A= 1064 nm) and its harmonics (A=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF; fragment ions, even at the lowest laser power densities at which signal could be detected. In general, the doubly charged uranium ion (U2+) intensity is much greater than that of the singly charged uranium ion (U+). For the case of the tunable dye laser experiments, the U n + (n = 1-4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The MPI-PES studies reveal only very slow electrons (,0.5 eV) for all wavelengths investigated. The dominance of the U2+ ion, the absence or very small intensities of UF; (x= 1-3) fragments, the unstructured wavelength dependence, and the preponderance of slow electrons all indicate that mechanisms may exist other than ionization of bare U atoms following the stepwise photodissociation of F atoms from the parent molecule. The data also argue against stepwise photodissociation of UF; (x = 5,6) ions. Neither of the traditional MPI mechanisms ("neutral ladder" or the "ionic ladder") are believed to adequately describe the ionization phe!lomena observed. We propose that the multiphoton excitation of UF 6 under these experimental conditions results in a highly excited molecule, superexcited UF:* . The excitation of highly excited UF:* is proposed to be facilitated by the well known "giant resonance," whose energy level lies in the range of 12-14 eV above that of ground state UF 6 . The highly excited molecule then primarily dissociates, via multiple channels, into U n +, UF;, fluorine atoms, and "slow" electrons, although dissociation into F-ions is not ruled out.

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Section: Discussionmentioning

confidence: 94%

Multiphoton ionization of uranium hexafluoride

Armstrong¹,

Harkins²,

Compton

et al. 1994

The Journal of Chemical Physics

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“…nf (n > 5) states all lie in the outer well eliminating the possibility of 5d-nf transitions. The 5 , f notation (Connerade et al 1980) is used to indicate the hybrid 5f/continuum nature of the high-energy resonance. An up to date discussion of the hybrid discrete/continuum nature of giant resonances is given in the paper of Kucas and Karazija (1998).…”

Section: Resultsmentioning

confidence: 99%

Application of a picosecond laser plasma continuum light source to a dual-laser plasma photoabsorption experiment

Meighan

Danson

Dardis

et al. 2000

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

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The characteristics of an extreme-ultraviolet (XUV) continuum light source and its application to a dual-laser plasma (DLP) photoabsorption experiment are described. The continuum emitting plasma was formed by focusing a 7 ps, 248 nm, 15 mJ laser pulse onto a number of selected targets known to be good XUV continuum emitters (Sm, W, Au and Pb), while the second absorbing plasma was produced by a 15 ns, 1064 nm, 300 mJ pulse. The duration of the continuum emission for these plasmas has a mean value of ∼150 ps, but depends on both the target material and the picosecond laser pulse energy. Using this picosecond DLP set-up we have been able to measure the photoabsorption spectrum of an actinide ion (thorium) for the first time.

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Giant Resonances in Atoms and in Fluorine Cage Molecules

Mansfield

1987

Giant Resonances in Atoms, Molecules, and Solids

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Experimental evidence for the existence of a overbar(5,ϵ)f resonantly localised continuum state in uranium

Cited by 23 publications

References 10 publications

Multiphoton ionization of uranium hexafluoride

Multiphoton ionization of uranium hexafluoride

Application of a picosecond laser plasma continuum light source to a dual-laser plasma photoabsorption experiment

Giant Resonances in Atoms and in Fluorine Cage Molecules

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