| 1. |
- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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| 2. |
- Balcou, P, et al.
(författare)
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High-order-harmonic generation: towards laser-induced phase-matching control and relativistic effects
- 2002
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 74:6, s. 509-515
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Tidskriftsartikel (refereegranskat)abstract
- We present a review of some recent results on high-order-harmonic generation, aiming at optimizing the photon flux to allow for future applications in extreme-ultra-violet non-linear optics. We first present new schemes to control phase matching of high harmonics in gases, by using the effect of the spatially varying atomic phase displayed by the high harmonics. An enhancement by a factor of 50 is observed in neon in conditions for which the gradient of the atomic dispersion balances the electronic dispersion. A new scheme to manipulate the laser field was demonstrated, and shown to improve phase matching. We then turn to high-harmonic generation by solid targets, and show that high harmonics generated by an intense 30-fs laser pulse remain collimated even at the threshold of the relativistic regime.
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| 3. |
- Gayou, O, et al.
(författare)
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Measurement of G(Ep)/G(Mp) in (e)over-right-arrowp -> e(p)over-right-arrow to Q(2)=5.6 GeV2
- 2002
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Ingår i: Physical Review Letters. - 1079-7114. ; 88:9
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Tidskriftsartikel (refereegranskat)abstract
- The ratio of the electric and magnetic form factors of the proton G(Ep)/G(Mp), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic (e) over right arrowp --> e (p) over right arrow reaction. The new data presented span the range 3.5 < Q(2) < 5.6 GeV2 and are well described by a linear Q(2) fit. Also, the ratio rootQ(2) F-2p/F-1p reaches a constant value above Q(2) = 2 GeV2.
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| 4. |
- Tcherbakoff, O., et al.
(författare)
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Controlling the duration of XUV high order harmonic pulses
- 2003
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Ingår i: 2003 Conference on Lasers and Electro-Optics Europe, CLEO/EUROPE 2003. - 0780377346 - 9780780377349
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Konferensbidrag (refereegranskat)abstract
- We modulate temporally the polarization of a ∼ 30 fs, 800 nm IR pulse and use it to generate high order harmonics. The harmonic emission can clearly be confined and the XUV pulse duration can be continuously tuned from - 5 - 7 fs to 50 fs.
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| 5. |
- Lopez, Rodrigo, et al.
(författare)
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Time-resolved ellipticity gating of high-order harmonic emission
- 2004
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Ingår i: Physical Review A. ; 69, s. 1-053811
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Tidskriftsartikel (refereegranskat)abstract
- We present time-resolved cross-correlation measurements of extreme ultraviolet (xuv) pulses generated as high-order harmonics of intense 35 fs pulses, using a short (12 fs) probe pulse. We modulate the ellipticity of the laser driving the generation process such that the polarization is linear for short times around the temporal peak of the pulse. Since harmonic generation is strongly suppressed for very small amounts of driving laser ellipticity, the emission of xuv radiation can therefore be confined to times much shorter than the laser pulse duration. In addition, our setup allows us to continuously confine the xuv emission as well as to determine its frequency sweep during the pulse.
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| 6. |
- Merdji, H., et al.
(författare)
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Coherence properties of high-order harmonics : Application to high-density laser-plasma diagnostic
- 2000
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 18:3, s. 495-502
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Tidskriftsartikel (refereegranskat)abstract
- We present two interferometry schemes in the extreme ultraviolet, based on either the wave-front division of a unique harmonic beam (1st scheme) or two spatially separated, phase-locked harmonic sources (2nd scheme). In the first scheme using a Fresnel bimirror interferometer, we measure the degree of spatial coherence of the 13 th harmonic generated in xenon, as a function of different parameters. A high degree of coherence, larger than 0.5, is found for the best conditions in almost the full section of the beam. Then, we demonstrate that the second scheme can be used for interferometry measurements with an ultrahigh time resolution. The 11th harmonic is used to study the spatial variation of the electron density of a laser-produced plasma. Electronic densities higher than 2.10 20 cm -3 are measured.
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| 7. |
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| 8. |
- O'Keeffe, P, et al.
(författare)
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Polarization effects in two-photon nonresonant ionization of argon with extreme-ultraviolet and infrared femtosecond pulses
- 2004
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 69:5
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of experimental and theoretical investigations of the two-color, two-photon ionization of Ar atoms, using femtosecond pulses of infrared laser radiation in combination with its extreme-ultraviolet harmonics. It is shown that the intensities of the photoelectron lines resulting from the absorption of photons from both fields strongly depend both on the respective phases of the fields and on atomic quantities such as the asymmetry parameter. These phases, which are notoriously difficult to measure, can be estimated by changing the polarization state of the laser radiation.
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| 9. |
- S. Zamith, V. Blanchet, B. Girard, J. Norin, J. Mauritsson, A. l'Huillier, J. Andersson, S. L. Sorensen, I. Hjelte, O. Björneholm and D. Gauyacq
(författare)
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The predissociation of highly excited states in acetylene by time-resolved photoelectron spectroscopy
- 2003
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Ingår i: Journal of Chemical Physics. ; :119, s. 3763-
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Sorensen, SL, et al.
(författare)
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Femtosecond pump-probe photoelectron spectroscopy of predissociative Rydberg states in acetylene
- 2000
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AMER INST PHYSICS. - 0021-9606. ; 112:18, s. 8038-8042 Language: English
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Tidskriftsartikel (refereegranskat)abstract
- We employ a pump-probe approach to molecular photoionization to study fast dissociation of Rydberg states in acetylene. By using time-resolved photoelectron spectroscopy to study the electronic state of the resulting ions we are able to monitor the system
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| 11. |
- Sorensen, S. L., et al.
(författare)
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Femtosecond pump-probe photoelectron spectroscopy of predissociative Rydberg states in acetylene
- 2000
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:18, s. 8038-8042
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Tidskriftsartikel (refereegranskat)abstract
- We employ a pump-probe approach to molecular photoionization to study fast dissociation of Rydberg states in acetylene. By using time-resolved photoelectron spectroscopy to study the electronic state of the resulting ions we are able to monitor the system continuously during dissociation or rearrangement. We find that the predissociative lifetime for the 3R‴ (v′2 = 1) Rydberg state is about 150 fs. We demonstrate a powerful new technique using time-correlated femtosecond harmonic generation and laser light pulses to study the time evolution of ultrafast dynamic processes in molecules.
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| 12. |
- Zair, A, et al.
(författare)
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Time-resolved measurements of high order harmonics confined by polarization gating
- 2004
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 78:7-8, s. 869-872
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the temporal confinement of high order harmonic pulses generated by a femtosecond (fs) infrared (IR) pulse with a time varying polarization. We use a set of two birefringent quartz plates to modulate the IR polarization. It produces a short temporal gate of linear polarization where harmonics are efficiently generated during a small fraction of the IR pulse. By rotating one of the plates, the gate width can be continuously varied between 70 fs down to 7 fs. The XUV pulse duration is measured by cross-correlation with a probe IR pulse of 12 fs. When the gate width is decreased, a clear temporal confinement of the XUV emission is observed through the cross correlation signal. This experiment is the first direct experimental evidence in the temporal domain that the polarization gating technique can be used to significantly shorten the harmonic pulse duration.
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