| 51. |
- Erman, P, et al.
(författare)
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Autoionization Widths of the No Rydberg-valence State Complex In the 11-12 Ev Region
- 1995
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 239:1-3, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- The photoion excitation spectra of (NO)-N-14 and (NO)-N-15 have been studied in the 105-112 Mn excitation region using high-order harmonic laser spectroscopy. Utilizing the small bandwidth offered by this technique, the natural widths of prominent lines in this region have been measured. These lines originate from interactions between high-lying Rydberg levels converging to the NO+ electronic ground state and a 'new' NO valence state situated close to the latter state. The present measurements show broad resonances corresponding to a decay time of 20-50 fs. This supports the interpretation that the decay takes place via rapid electronic autoionization.
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| 52. |
- Faldon, M. E, et al.
(författare)
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Studies of time-resolved harmonic generation in intense laser fields in xenon
- 1992
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 9:11, s. 2094-2099
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Tidskriftsartikel (refereegranskat)abstract
- We report preliminary experimental and computational studies of the temporal evolution of the harmonics, generated in xenon, by 50-ps pulses from a Nd: YLF laser, amplified in Nd: glass amplifiers, and focused to produce intensities in the range 1013--5 {\texttimes} 1013 W cm{\textminus}2. Measurements were made of the temporal profiles of the seventh- and ninth-order harmonics using a specially modified VUV streak camera with better than 7-ps temporal resolution. These results were compared with predictions of a numerical model that included the effects of neutral atom depletion and photoelectron dispersion in the calculation of the harmonic output as a function of time.
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| 53. |
- Fill, E, et al.
(författare)
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Xuv Spectra of Optical-field-ionized Plasmas
- 1995
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Ingår i: Physical Review E: covering statistical, nonlinear, biological, and soft matter physics. - 1063-651X. ; 51:6, s. 6016-6027
-
Tidskriftsartikel (refereegranskat)
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| 54. |
- Frasinski, L. J, et al.
(författare)
-
Multielectron Dissociative Ionization of Co2 In Intense Laser Fields
- 1994
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 27:6, s. 97-109
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Tidskriftsartikel (refereegranskat)abstract
- The multiphoton ionization of CO2 has been studied using a laser of 794 nm WaVelength and focused intensities in the region of 10(16) W cm-2. The kinetic energy distributions and ion yields obtained using time-of-flight spectroscopy coupled with covariance mapping can be interpreted most simply in terms of charge-symmetric fragmentation, the strongest channel being O2+ + C2+ + O2+. These results are compared with two recent experiments on CO2, one using an intense laser at 248 nm, the other using Si8+ ion projectiles of 3 MeV u-1 energy.
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| 55. |
- Fullagar, Wilfred, et al.
(författare)
-
A broadband laser plasma X-ray source for application in ultrafast chemical structure dynamics
- 2007
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 78:11, s. 1-115105
-
Tidskriftsartikel (refereegranskat)abstract
- A plasma source free from characteristic emission lines is described, based on laser irradiation of a water jet in a helium atmosphere. Various key aspects of the laser interaction are presented along with practical characterization of the observed isotropic ~4–10 keV x-ray emissions, measurements of which indicate subpicosecond duration. Observations are consistent with a vacuum heating plasma mechanism at the helium-water interface and indicate strong potential for in-house ultrafast chemical structure dynamics application when coupled to contemporary detector developments.
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| 56. |
- Fullagar, Wilfred, et al.
(författare)
-
Lab-based Ultrafast Molecular Structure.
- 2010
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 1234, s. 919-922
-
Konferensbidrag (refereegranskat)abstract
- The proliferation of various laser-driven approaches to sub-picosecond hard X-ray and short-wavelength radiation generation in the past few decades has opened many avenues for the laboratory-based development of traditionally facility-based short wavelength ultrafast molecular structure science. Together with the introduction of microcalorimeter detection schemes, this opens the floodgates to widespread, decentralized implementation of what were until recently specialist short wavelength techniques. A parallel situation exists for the contemporary adoption of sub-wavelength resolution optical microscopies. In what follows, a few ultrafast molecular structure developments and their rationale are briefly recounted.
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| 57. |
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| 58. |
- Gaarde, Mette, et al.
(författare)
-
High-order tunable sum and difference frequency mixing in the xuv region
- 1996
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 29:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present a study of tunable high-order sum and difference frequency mixing in the 7-70 eV range, in xenon, argon and neon. We mix the light from a terawatt, subpicosecond titanium-sapphire laser and that from a tunable optical parametric generator. The radiation generated through mixing processes involves absorption or emission of one or Mo photons from the weak tunable source. The relative strengths of the sum and difference frequency processes depend strongly on the wavelength range of the generated radiation. The sum frequency processes are stronger at low photon energies in xenon, whereas the difference frequency processes dominate at high photon energies, in neon, being almost comparable to harmonic generation.
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| 59. |
- Gahn, C, et al.
(författare)
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Generating positrons with femtosecond-laser pulses
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:17, s. 2662-2664
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing a femtosecond table-top laser system, we have succeeded in converting via electron acceleration in a plasma channel, low-energy photons into antiparticles, namely positrons. The average intensity of this source of positrons is estimated to be equivalent to 2x10(8) Bq and it exhibits a very favorable scaling for higher laser intensities. The advent of positron production utilizing femtosecond laser pulses may be the forerunner to a table-top positron source appropriate for applications in material science, and fundamental physics research like positronium spectroscopy. (C) 2000 American Institute of Physics. [S0003-6951(00)00143-1].
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| 60. |
- Gahn, C, et al.
(författare)
-
Generation of MeV electrons and positrons with femtosecond pulses from a table-top laser system
- 2002
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 9:3, s. 987-999
-
Tidskriftsartikel (refereegranskat)abstract
- In experiments, the feasibility was demonstrated of generating multi-MeV electrons in a form of a collimated beam utilizing a table-top laser system delivering 200 fs pulses with P-L=1.2 TW and 10 Hz capability. The method uses the process of relativistic self-channeling in a high-density gas jet producing electron densities in the range of 3x10(19)-6x10(20) cm(-3). In a thorough investigation, angularly resolved and absolutely calibrated electron spectra were measured and their dependence on the plasma density, laser intensity, and gas medium was studied. For the optimum electron density of n(e)=2x10(20) cm(-3) the effective temperature of the electron energy distribution and the channel length exhibit a maximum of 5 MeV and 400 mum respectively. The laser-energy to-MeV-electron efficiency is estimated to be 5%. In a second step, utilizing the multi-MeV electron beam anti-particles, namely positrons, were successfully generated in a 2 mm Pb converter. The average intensity of this new source of positrons is estimated to be equivalent to a radioactivity of 2x10(8) Bq and it exhibits a very favorable scaling for higher laser intensities. (C) 2002 American Institute of Physics.
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