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131.
B.?Smeets Email author R.C.M.?Bosch P.?van der Straten E.?te Sligte R.E.?Scholten H.C.W.?Beijerinck K.A.H.?van Leeuwen 《Applied physics. B, Lasers and optics》2003,76(8):815-819
Polarization spectroscopy of an Fe-Ar hollow cathode discharge cell was used to lock a frequency-doubled Ti:sapphire laser to the 372-nm5D45F5 transition of 56Fe. The discharge cell produced a density of 1018 m-3 ground-state 56Fe atoms at a temperature of 650 K, this density being comparable to a conventional oven at 1500 K. Saturated absorption spectroscopy and two schemes of polarization spectroscopy were compared with respect to signal-to-background ratio and the effect of velocity-changing collisions. The laser was locked within 0.2 MHz for hours by feedback of the dispersive polarization spectroscopy signal. PACS 33.55.Ad; 42.62.Fi; 52.25.Ya 相似文献
132.
B. Ramstein C. Mosbacher T. Hennino W. Augustyniak D. Bachelier H.G. Bohlen J.L. Boyard R. Dahl C. Ellegaard C. Gaarde J. Gosset J.C. Jourdain J.S. Larsen M.C. Lemaire D. L'Hôte H.P. Morsch M. Österlund J. Poitou P. Radvanyi M. Roy-Stephan T. Sams M. Skousen S. Tarlé-Rousteau P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):583-597
The exclusive 2H( 3He, t)2p reaction has been studied at 2 GeV for energy transfers up to 500 MeV and triton angles up to 3.4°. The protons were measured in the large acceptance magnetic detector DIOGENE, in coincidence with the forward tritons detected
in a dedicated magnetic arm. The energy transfer spectra extend well above the pion threshold. However, in the region of Δ
excitation, the yield is less than 10% of the inclusive 2H( 3He, t) cross-section, which indicates the small contribution of the ΔN ↦ NN process. The angular distributions of the two
protons in their center of mass have been analysed as a function of energy transfer and triton angle and a Legendre polynomial
decomposition has been achieved. These data have been compared to a model based on a coupled-channel approach for describing
the NN and NΔ systems.
Received: 21 October 2002 / Accepted: 15 November 2002 / Published online: 11 March 2003
RID="a"
ID="a"e-mail: ramstein@ipno.in2p3.fr
RID="†"
ID="†"Deceased.
RID="†"
ID="†"Deceased.
RID="d"
ID="d"Present adress: School of Engineering, J?nk?ping University, P.O. Box 1026, S-551 11 J?nk?ping, Sweden.
Communicated by M. Gar?on 相似文献
133.
Dupont J Déroussiaux A Coquard M Lavorel B Faucher O Loëte M Jauslin HR 《Journal of Molecular Spectroscopy》2000,199(2):252-258
We report a theoretical and experimental investigation of the dynamical Stark effect in a tetrahedral molecule, silane (SiH(4)). We use a tetrahedral formalism and Floquet theory to calculate the absorption spectra for the molecule dressed by an intense nonresonant pulsed laser. Experimentally, the dynamical Stark effect is observed for transitions of the nu(2)/nu(4) vibrational polyad of SiH(4) by means of nanosecond diode laser absorption spectroscopy and a Nd:YAG laser excitation. Copyright 2000 Academic Press. 相似文献
134.
The specific heat has been measured of powdered samples of NiX2L2 (X = Cl, Br; L = pyrazole, pyridine), compounds which can be considered as weakly antiferromagnetically coupled ferromagnetic chains with large uniaxial single-ion anisotropy. The intrachain exchange constants and the zero-field splitting parameters for the four compounds have been deduced from the specific heat data, using accurate numerical calculations for the isotropic Heisenberg spin S = 1 linear chain model with uniaxial single-ion anisotropy. 相似文献
135.
136.
137.
138.
Leca D Song K Amatore M Fensterbank L Lacôte E Malacria M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(4):906-916
Reaction of sulfonamides with iodosobenzene leads to phenyliodinanes. A new catalysis reaction of the decomposition of these products in the presence of sulfoxides that allows the smooth synthesis of sulfoximines has been evidenced and studied: copper(II) salts were used to prepare compounds 4 a-j and 5 b, d, f, j, k from the corresponding, easily prepared, sulfoxides. The reactions proceed with retention of configuration at the sulfur center, and copper(II) triflate is the best candidate for the catalyst for the imination. Switching from sulfonamides to sulfinamides in the preparation of the starting iodinanes completely alters the reaction pathway: iodinanes are no longer accessible, and sulfonimidates 7 a-j are obtained instead. This behavior can be rationalized by the increase in pK(a) brought about by the removal of one oxygen atom from the sulfur center. Sulfonimidates are interesting molecules with varied applications. Optimization of their one-pot synthesis has been achieved by carrying out the reaction in acetonitrile. The stereochemical study has shown that the transformation proceeds with global retention of the configuration at the sulfur center, albeit with erosion of the enantiomeric purity. A model accounting for this outcome is proposed. In addition, the presence of oxidized sulfonamide by-products has been explained, and this latter pathway becomes the sole one when alcohol is replaced by water. Good yields of the oxidized products are obtained. 相似文献
139.
Tuning and stability of a continuous-wave mid-infrared high-power single resonant optical parametric oscillator 总被引:1,自引:0,他引:1
M.M.J.W. van Herpen S. Li S.E. Bisson S. te Lintel Hekkert F.J.M. Harren 《Applied physics. B, Lasers and optics》2002,75(2-3):329-333
A 2.2-W continuous-wave, continuously tunable, single-frequency OPO has been developed in the 3.0–3.8 μm wavelength range
for the detection of molecular trace gasses. The oscillation threshold, output power and stability of the single resonant
OPO were improved by optimizing pump beam waist and OPO cavity length. Both air-spaced and solid etalons were tested to frequency
stabilize and tune the OPO, from which the solid etalon gave a better performance. Temperature oscillations in the PPLN crystal
caused oscillations in the idler wavelength of less than 200 MHz over 300 s; the short-term stability was less than 3 MHz
over 1 s. The high laser power, in combination with photoacoustic spectroscopy, achieved a detection limit of 10 parts-per-trillion
for ethane in nitrogen.
Received: 9 April 2002 / Revised version: 14 June 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax:+31-24/3653311, E-Mail: maartenh@sci.kun.nl 相似文献
140.
te Nijenhuis B Heutinck K van Schijndel B 《Fresenius' Journal of Analytical Chemistry》2001,369(7-8):741-743
Participation in proficiency testing schemes (PT-schemes) is an important way to prove and to improve the skills of analytical chemical students. It gives valuable information on the professional capabilities of the students and is thus an important step in the training of laboratory engineers and technicians. In the programme described three types of samples are offered to the students: chemical, environmental and clinical samples. A guiding protocol presents instructions to the participating student groups. Standard operating procedures are available, but the students are also free to select their own method. The results are methodologically and statistically judged by professional PT-organisers and are presented in the customary way: the dataset, the mean (consensus) value of all participants and the Z-scores. The final presentation of the results takes place in an annual symposium where awards are presented to the best performing student groups, and a lecture programme is presented with subjects in the area of quality assurance and quality control. A selection of results from the KILO/PT/1998-1999 and the KILO/PT/1999-2000 programme is presented. 相似文献