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1.
We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of
three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of ∼1.5 × 104 J cm − 2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions
decreases on decreasing the laser pulse duration, even though the peak laser intensities of 3.5 × 1017 W cm − 2 for the 45 fs pulses and 6.2 × 1014 W cm − 2 for the 25 ps pulses are much higher than 5 × 1012 W cm − 2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization
states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse
intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma. 相似文献
2.
D. Lunney G. Audi C. Gaulard M. de Saint Simon C. Thibault N. Vieira 《The European Physical Journal A - Hadrons and Nuclei》2006,28(2):129-138
High-precision mass measurements have been performed on the exotic magnesium isotopes 29-33Mg using the MISTRAL radiofrequency spectrometer, especially suited for very short-lived nuclides. This method, combined with
the powerful tool of resonant laser ionization at ISOLDE, has provided a significant reduction of uncertainty for the masses
of the most exotic Mg isotopes: a relative error of 7×10-7 was achieved for the weakly produced 33Mg that has a half-life of only 90ms. Moreover, the mass of 33Mg is found to change by over 250keV. Verifying and minimizing binding energy uncertainties in this region of the nuclear
chart is important for understanding the lack of binding energy that is normally associated with magic numbers. 相似文献
3.
Absolute measurement for He-α resonance (1s2 1S0?1s2p1 P 1, at 40.2 Å) line emission from a laser-produced carbon plasma has been studied as a function of laser intensity. The optimum laser intensity is found to be ≈1.3×1012 W/cm2 for the maximum emission of 3.2 × 1013 photons sr?1 pulse?1. Since this line lies in the water window spectral region, it has potential application in x-ray microscopic imaging of biological sample in wet condition. Theoretical calculation using corona model for the emission of this line is also carried out with appropriate ionization and radiative recombination rate coefficients 相似文献
4.
The detection of long-lived plutonium isotopes in ultra-trace amounts by resonance ionization mass spectrometry (RIMS) is
a well-established routine method. Detection limits of 106 to 107 atoms and precise measurements of the isotopic composition have been achieved. In this work multi-step resonance ionization
of plutonium atoms has been performed with tunable lasers having very different output intensities and spectral properties.
In order to compare different ways for the resonance ionization of plutonium broadband pulsed dye and titanium:sapphire lasers
as well as narrow-band cw-diode and titanium:sapphire lasers have been applied for a number of efficient excitation schemes.
It has been shown, that for identical excitation schemes the optical isotope selectivity can be improved by using cw-lasers
(bandwidths < 10 MHz) instead of pulsed lasers (bandwidths > 2 GHz). Pulsed and cw-laser systems have been used simultaneously
for resonance ionization enabling direct comparisons of pulsed and continuous ionization processes. So far, a three-step,
three-color laser excitation scheme has been proven to be most practical in terms of efficiency, selectivity and laser wavelengths.
Alternatively a newly discovered three-step, two-color excitation scheme which includes a strong two-photon transition from
an excited state into a high-lying autoionizing state yields similar ionization efficiencies. This two-photon transition was
characterized with respect to saturation behavior and line width. 相似文献
5.
M. Seliverstov A. Andreyev N. Barré H. De Witte D. Fedorov V. Fedoseyev S. Franchoo J. Genevey G. Huber M. Huyse U. Köster P. Kunz S. Lesher B. Marsh B. Roussière J. Sauvage P. Van Duppen Yu. Volkov 《Hyperfine Interactions》2006,171(1-3):225-231
Mean-square charge radii and magnetic moments have been measured for the neutron deficient lead isotopes, 182–190Pb. The measurement was performed at the ISOLDE online mass separator, using the in-source resonance ionization spectroscopy
technique. The wavelength of the first excitation step for the resonance ionization laser ion source (RILIS) was scanned over
the resonance(s) whilst the α- and γ-ray spectra from the decay of the Pb isotopes were recorded as a function of the wavelength. The isotope shift and, in the
case of odd-A isotopes, the hyperfine splitting were deduced. The rms-charge radii of the very neutron deficient Pb isotopes follow the
smooth trend of the heavier isotopes. This finding indicates a spherical shape for the lead ground states at the neutron mid-shell
(N = 104), where the excitation energy of the oblate 0+ state in the even isotopes reaches its minimum. 相似文献
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《Nuclear Physics A》1988,486(2):278-284
The internal ionization accompanying the first-forbidden unique electron-capture decay of 41Ca was investigated. The integrated probability of electron ejection with energy greater than 38keV was found to be (0.17 ± 0.02) × 10−5 per K-capture. In this energy range, the measured spectrum of ejected electrons is fairly close to predictions of the simple theory of Primakoff and Porter, and of the relativistic theory of Mukoyama et al. By a model-dependent extrapolation of this spectrum toward low energies, the total probability of internal ionization in 41Ca was estimated and compared with relevant experimental results for other isotopes. 相似文献
9.
H. Backe P. Graffé D. Habs M. Hies Ch. Illgner H. Kunz W. Lauth H. Schöpe P. Schwamb W. Theobald P. Thörle N. Trautmann R. Zahn 《Hyperfine Interactions》1993,78(1-4):35-45
An ultra-sensitive laser spectroscopic method has been developed for the hyperfine spectroscopy of short-lived isotopes far off stability produced by heavy ion induced nuclear reactions at very weak intensity (> 1/s). It is based on resonance ionization spectroscopy in a buffer gas cell with radiation detection of the ionization process (RADRIS). As a first on-line application of RADRIS optical spectroscopy at242fAm fission isomers is in progress at the low target production rate of 10/s. The resonance ionization has been performed in two steps utilizing an excimer dye laser combination with a repetition rate of 300 Hz. The first resonant step proceeds through terms which correspond to wavelengths of 466.28, 468.17 or 426.56 nm; the second non-resonant step is achieved with the 351 nm radiation of the excimer laser itself, running with XeF. The frequency scans of the tuneable dye laser at 466.28 and 468.17 nm exhibit broad resonance ionization signals, the latter with a large isotope shift between242fAm and243Am which is in accordance with the large quadrupole moment of the242fAm fission isomer.Work supported by the Bundesministerium für Forschung und Technologie under contract 06 MZ 188 I. 相似文献
10.
A. E. Barzakh D. V. Fedorov V. S. Ivanov K. A. Mezilev P. L. Molkanov F. V. Moroz S. Yu. Orlov V. N. Panteleev Yu. M. Volkov 《Hyperfine Interactions》2013,216(1-3):27-31
A new laser installation for the resonance ionization spectroscopy in a laser ion source and for rare isotope production has been put into operation at the IRIS mass-separator, working on-line with the 1 GeV proton beam of the Petersburg Nuclear Physics Institute synchrocyclotron. Isotope shift and hyperfine splitting of 276.9 nm atomic transition in the long chain of Tl isotopes and isomers have been measured. New data on the magnetic moments and changes in mean squared charge radius for 183,184,185,185m,186m2,195m,197mTl have been obtained. 相似文献
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We present in this work a new experimental set-up for sensitive detection of reactive species: continuous wave cavity ring-down spectroscopy (cw-CRDS) as a detection method in laser photolysis reactor. HO2 radicals were generated by using a 248 nm photolysis of SOCl2/CH3OH/O2 mixtures and were detected in the first vibrational overtone of the OH stretch around 6625 cm-1, using a DFB diode laser. In order to perform the spectroscopic and kinetic measurements of the HO2 radical, two different timing schemes have been used. The absorption line strength of the transition at 6625.784 cm-1 has been extracted from kinetic measurement to (5.2±1.0)×10-21 cm2 molecule-1cm-1. The detection limit for the actual set-up is 2×1012 molecules cm-3. PACS 42.62.Fi; 82.33.Tb; 82.20.W 相似文献
13.
Klaus D. A. Wendt Klaus Blaum Christopher Geppert Peter Müller Wilfried Nörtershäuser Annette Schmitt Philipp Schumann Norbert Trautmann Bruce A. Bushaw 《Hyperfine Interactions》2005,162(1-4):147-157
A variety of research activities in the field of fundamental and applied nuclear physics has evolved in the last years using
resonantly tuned radiation from powerful lasers. The technique of resonance ionization spectroscopy has delivered outstanding
results and found broad acceptance in the last years as a particularly efficient and highly selective method for rare and
exotic radioisotope studies. It is used for production, spectroscopy and detection of these species and provides complete
isobaric, high isotopic and even some isomeric selection, which altogether is needed for on-line investigation of short lived
species far off stability as well as for ultra trace determination. Good overall efficiency pushes the experimental limits
of detection in elemental trace analysis down to below 106 atoms per sample, and additionally isotopic selectivity as high as 3 × 1012 has been demonstrated. The widespread potential of resonance ionization techniques is discussed, focusing on the experimental
arrangements for applications in selective on-line isotope production, spectroscopy of rare radioisotopes and ultra trace
determination of radiotoxic isotopes like 238Pu to 244Pu, 135,137Cs, 89,90Sr or 41Ca in environmental, technical and biomedical samples. 相似文献
14.
A theory of thermonuclear fusion caused by the irradiation of deuterium-iodide clusters with the field of a superatomic femtosecond laser pulse is developed. It is based on considering the process in which the sequential above-barrier multiple internal ionization of atomic ions within a cluster is accompanied by external field ionization. The theory is illustrated by taking the example of a cluster that is formed by 106 molecules of deuterium iodide and which is irradiated with a laser pulse of duration 50 fs and intensity 2×1018 W/cm2 at the peak. This case is dominated by I26+ atomic ions. The yield of neutrons from thermonuclear fusion in a deuteron-deuteron collision upon the passage of a laser pulse is calculated. The result is 105 neutrons per laser pulse. The mean kinetic energy of deuterons is estimated at 50 keV. Owing to induced inverse bremsstrahlung in scattering on multiply charged atomic ions, the electron temperature increases up to 28 keV. The role of the Mie resonance in the heating of the electron component is discussed. 相似文献
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A theory is developed for calculating the charge composition of a cluster plasma produced upon irradiation of large atomic clusters by the field of a superatomic femtosecond laser pulse. The theory is based on the overbarrier process of a successive multiple internal ionization of atomic ions inside a cluster accompanied by the external field ionization. Collision ionization is also taken into account in the calculations. The theory is illustrated by the example of a cluster consisting of 106 xenon atoms irradiated by a 50-fs laser pulse with a peak intensity of 2×1018 W/cm2. In this case, the Xe26+ ions dominate. The amounts of atomic xenon ions with multiplicity up to 31 are calculated. 相似文献
18.
Propagation regimes of a plasma (fast ionization wave, laser-supported radiation wave, and laser-supported detonation wave) generated by laser radiation in a wide range of intensities (5 × 108?1011 W/cm2 ) are described. The regimes were analyzed on the basis of the calculated dependence of the propagation velocity on the laser radiation intensity. The lower bound of the velocity was used for the fast ionization wave. Calculation results agree with experimental data and show that the plasma propagates as a fast ionization wave in the above range of intensities. 相似文献
19.
Yu. A. Kudryavtsev 《Hyperfine Interactions》1992,74(1-4):169-180
Results are presented of the work on the development of a method for detecting ultra rare isotopes, based on the collinear
isotope-selective laser ionization of atoms in a fast bearn. The rare isotope3He was detected at a selectivity of 109 and isotope-selective ionization of krypton atoms was demonstrated. A scheme is suggested for detecting the rare radioactive
isotopes85Kr and81Kr. The technique has been exploited for the measurement of hyperfine structures and isotope shifts of unstable Yb isotopes. 相似文献
20.
A dual-beam laser absorption spectrometer with balanced detection for high sensitivity detection of oxygen via the A-band
at 760 nm is described. The 2×2 vertical-cavity surface-emitting laser arrays used for this set-up are characterized by their
wavelength tuning behavior with temperature and current, amplitude modulation, side-mode suppression ratio and polarization
contrast. The spectrometer performance is determined over time periods of up to 10 h using the variation in the differential
absorption between two beam paths. With the R11R11 line at STP, 670 μW laser power and 200 mm-long absorption cells, we realized
an excellent linearity (R=0.9999) and over a 5-min interval a record sensitivity for VCSEL-based spectrometers of 35 ppmV,
corresponding to an optical density (O.D.) of 7×10-7. For this specific set-up, this sensitivity is only a factor of 2.7 above the shot noise limit, giving us a normalized detection
limit of 7.6 ppmV·m·. Over a 10-h interval we achieved a standard deviation of 65 ppmV.
Received: 26 July 2000 / Revised version: 1 November 2000 / Published online: 6 December 2000 相似文献