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141.
142.
Gavin R. Caine Simon J. Dunne Ellak I. Von Nagy-Felsobuki 《Journal of heterocyclic chemistry》1995,32(1):89-96
The He I and He II ultraviolet photoelectron spectra of 2-fluoro-, 2-chloro-, 2-bromo-, and 2-iodopyridine have been recorded and interpreted in terms of a composite-molecule model. The sequence of the four lowest ionization energies for 2-fluoro- and 2-chloropyridine is: π3 (1a2) > nN (11a1) > π2 (2b1) > πpyr (7b2), whereas for 2-bromo- and 2-iodopyridine the assignment is: π3 (1a2) - πX > nN (11a1) > πX > π2 (2b1), where X represents a bromine and iodine lone-pair. Comparison of the He I and He II band intensities confirmed this assignment. However, ab initio calculations at the STO-3G*/STO-3G* and 6–31G**/STO-3G* levels did not agree with the sequence predicted by either the composite-molecule model, simple correlations and the He I/He II cross-section ratios. For the 2-fluoropyridine, a comparison using the HAM/3 model was found to be in agreement with this assignment. 相似文献
143.
The 4He(3He, n)6Be reaction has been investigated at 36.20 MeV bombarding energy in search for a narrow resonance near the 3He-3He threshold which has been proposed as a possible explanation for the missing solar neutrinos in Davis' experiment. Neutrons have been detected at θb = 0° with an effective resolution < 25 keV in the c.m. system, in coincidence with protons emitted at θp = 50°. No indication for the existence of such a resonance has been found and an upper limit (dσ/dω)res ≦ 7.5 μb/sr has been established. 相似文献
144.
H.W. Atherton C. Bovet P. Coet R. Desalvo N. Doble R. Maleyran E.W. Anderson G. Von Dardel K. Kulka M. Boratav J.W. Cronin B.D. Milliken 《Physics letters. [Part B]》1985,158(1):81-84
The lifetime of the neutral pion (π0) has been directly measured. The lifetime has been found to be τπ0 = (0.897±0.022±0.017) × 10?16 s. The systematic error results from uncertainties in the momentum spectrum of the π0 used for the measurement. This measurement yields a decay width of the π0 of (7.34±0.18±0.11) eV. An axial anomaly calculation, which neglects the finite mass of the π0, predicts a value of 7.87 eV. 相似文献
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148.
R. Von Der Mühll J. Ravez P. Hagenmuller P. Barbier M. Drache G. Mairesse 《Solid State Communications》1982,43(11):797-799
X-ray diffraction, calorimetric, dielectric and thermocurrent measurements have been carried out on Cs3BiCl6 ceramic samples. Three phase transitions have been detected at T1 = 395 K, T2 = 684 K and T3 = 727 K. The T3 transition is of ferroelastic-paraelastic type. The low temperature phase is characterized by remanent polarization. The depolarization current results probably from charge traps in potential minima which disappear at rising temperature. 相似文献
149.
A. Von Engel 《Applied Scientific Research》1956,5(1):34-42
Summary A short survey is given of the work of measuring and analyzing the radiation in the far u.v. which originates in the gas of an electric discharge. A new method is briefly described including some preliminary results. 相似文献
150.