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661.
The scattering of low energy (0.8 to 15.6 eV) electrons by TIF beans has been measured by beam recoil. Monomer concentrations are calculated and an overestimate of the monomers scattering is subtracted off. Analysis of the dimer component scattering indicates an instantaneous dipole moment of several debye. This result is not easily reconciled with a stiff symmetric linear structure for the dimer. 相似文献
662.
663.
664.
Properties of the positive column of low pressure Hg/Ar discharge have been investigated from the point of view of its application in fluorescent lamps. The results obtained are based on experimental methods to determine both UV resonance radiation fluxes of the 63 P1 and 61P1 Hg levels and to measure the electron distribution function by probes; in addition a kinetic model is applied for the theoretical interpretation of the experimental results and to give a deeper insight into the particle and energy budget. In the present first part of the paper the effects of recently determined τeff-values on radiation, net collision rates, power transfer and the electron energy distribution for extended parameter values are investigated especially in dependence on mercury partial pressure. 相似文献
665.
A series of unconventional twisted pi-electron system molecules has been synthesized via Suzuki cross-coupling of two sterically hindered arenes. Crystallographic analysis of these molecules reveals a large ring-ring dihedral twist angle (87 degrees ) and a highly charge-separated zwitterionic ground state. An efficient conversion of phenols into aryl halides is also reported. [reaction: see text] 相似文献
666.
667.
Measurements of coherent electron spin dynamics in Ga1-xMnxAs/Al0.4Ga0.6As quantum wells with 0.0006%相似文献
668.
We evaluate improvements in information capacity gained by use of time-division multiplexing (TDM) in three-dimensional integral imaging (II) systems. This analysis supports the motivation for two TDM methods in II [Opt. Lett. 27, 324 (2002); 1144 (2002)] that we previously developed. 相似文献
669.
S. Descotes-Genon L. Girlanda J. Stern 《The European Physical Journal C - Particles and Fields》2003,27(1):115-134
Multi-flavour chiral perturbation theory (PT) may exhibit instabilities due to vacuum fluctuations of sea pairs. Keeping the fluctuations small would require a very precise fine tuning of the low-energy constants and to , . A small deviation from these critical values - like the one suggested by the phenomenology of OZI-rule violation in the
scalar channel - is amplified by huge numerical factors inducing large effects of vacuum fluctuations. This would lead in
particular to a strong Nf dependence of chiral symmetry breaking (SB) and a suppression of the multi-flavour chiral order parameters. A simple resummation is shown to cure the instability
of PT, but it modifies the standard expressions of some O(p
2
) and O(p
4
) low-energy parameters in terms of observables. On the other hand, for r= m
s
/m > 15, the two-flavour condensate is not suppressed, due to the contribution induced by massive vacuum pairs. Thanks to the latter, the standard two-flavour PT is protected from multi-flavour instabilities and could provide a well-defined expansion scheme in powers of non-strange
quark masses.
Received: 31 July 2002 / Revised version: 6 November 2002 / Published online: 15 January 2003
RID="a"
ID="a" e-mail: sdg@hep.phys.soton.ac.uk
RID="b"
ID="b" e-mail: luca.girlanda@pd.infn.it * Present address: ECT*, Villa Tambosi, Strada delle Tabarelle 286, 38050 Trento, Italy
RID="c"
ID="c" e-mail: stern@ipno.in2p3.fr 相似文献
670.
Formaggio JA Yu J Adams T Alton A Avvakumov S de Barbaro L de Barbaro P Bernstein RH Bodek A Bolton T Brau J Buchholz D Budd H Bugel L Conrad JM Drucker RB Fleming BT Foster J Frey R Goldman J Goncharov M Harris DA Johnson RA Kim JH Koutsoliotas S Lamm MJ Marsh W Mason D McDonald J McFarland KS McNulty C Naples D Nienaber P Romosan A Sakumoto WK Schellman HM Shaevitz MH Spentzouris P Stern EG Suwonjandee N Vakili M Vaitaitis A Yang UK Zeller GP Zimmerman ED 《Physical review letters》2001,87(7):071803
The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process nu(mu)e(-)-->mu(-)nu(e), and to measure the cross section of the standard model inverse muon decay process nu(mu)e(-)-->mu(-)nu(e). NuTeV measures the inverse muon decay asymptotic cross-section slope sigma/E to be (13.8 +/- 1.2 +/- 1.4) x 10(-42) cm(2)/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the cross-section ratio sigma(nu(mu)e(-)-->mu(-)nu(e))/sigma(nu(mu)e(-)-->mu(-)nu(e)) < or = 1.7% at 90% C.L. for V-A couplings and < or = 0.6% for scalar couplings. 相似文献