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1.
[reaction: see text] The gas-phase thermal isomerization of cis,anti,cis-tricyclo[6.3.0.0(2,7)]undec-3-ene (1) to endo-tricyclo[5.2.2.0(2,6)]undec-8-ene (2) at 315 degrees C occurs cleanly through a symmetry-forbidden [1,3] suprafacial,retention (sr) pathway. 相似文献
2.
3.
J.M. Nitschke M. Fowler A. Ghiorso R.E. Leber M.E. Leino M.J. Nurmia L.P. Somerville K.E. Williams E.K. Hulet J.H. Landrum R.W. Lougheed J.F. Wild C.E. Bemis R.J. Silva P. Eskola 《Nuclear Physics A》1981,352(1):138-146
A rotating drum system was used to search for an 80 ms spontaneous fission (sf) activity in the reaction of 15N with 249Bk. No such activity was found beyond a cross section limit of 0.5 nb. A sf activity with a half-life of 23 ± 2 ms and a maximum formation cross section of 19 ± 4 nb at 82 MeV was observed. The identity of this activity has not been determined. 相似文献
4.
James F. Woodward André de Klerk Gail Kahler Kathrine Leber Peter Pompei Daniel Schultz Sharon Stern 《Foundations of Physics》1972,2(2-3):241-244
An experiment designed to test the highly speculative hypothesis of photon consciousness was executed. It was found that, within the accuracy attainable with the apparatus, there is no empirical justification for the hypothesis. 相似文献
5.
S. S. Barshay R. E. Leber R. M. Lambrecht 《Applied Physics A: Materials Science & Processing》1974,5(1):67-70
The Doppler broadening of positron annihilation photons was measured in 17 metals. A model which considers the positron lifetime spectra in metals to be composed of terms for annihilation with conduction and core electrons and surface centers of low electron momentum is used to correlate calculated core annihilation rates with the Doppler lineshape. Ta metal was doped with defects with high energy implantations of14N+4 ions at variable doses. Differences in the Doppler linewidths were ascribed as being principally a reflection of the probabilty of annihilation with core electrons relative to annihilation with conduction electrons. 相似文献
6.
J.M. Weber E. Leber M.-W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(4):587-594
Using a high resolution laser photoelectron attachment method, we have studied the formation of (H
2
O)
q
- (q = 2, 6, 7, 11, 15) cluster ions in collisions of slow free electrons (E = 1-80 meV) and Rydberg electrons (n = 12-300) with water clusters. Resonances at zero energy have been observed, the shapes of which are strongly dependent on
cluster size. The results are discussed in terms of the formation of metastable negative ions.
Received 8 March 1999 相似文献
7.
G. D. Barr P. Buchholz D. Cundy N. Doble L. Gatignon P. Grafström R. Hagelberg H. Wahl K. J. Peach T. Beier H. Blümer D. Coward R. Heinz K. Kleinknecht F. Leber P. Mayer B. Renk H. Rohrer H. G. Sander J. Scheidt J. Staeck A. Wagner E. Augé D. Fournier L. Iconomidou-Fayard O. Perdereau A. C. Schaffer L. Serin L. Bertanza P. Calafiura M. Calvetti R. Carosi R. Casali C. Cerri I. Mannelli V. M. Marzulli A. Nappi G. M. Pierazzini M. Holder A. Kreutz M. Rost R. Werthenbach 《Zeitschrift fur Physik C Particles and Fields》1995,65(3):361-365
Data from the NA31 experiment at CERN have been used to measure the branching ratio of the double Dalitz decay of the long-lived neutral kaon. Eight events have been found with negligible background. The measured distribution of the angle between the planes of the two e+e?-pairs favours aCP=?1 state for the long-lived neutral kaon. 相似文献
8.
N. A. Wogman L. J. Bond A. E. Waltar R. E. Leber 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(1):137-143
Summary The U.S. Department of Energy supports 24 fellowships for students to attend six-week programs at either San Jose State University in California, or Brookhaven National Laboratory (BNL) in New York. The American Chemical Society through the Division of Nuclear Science and Technology operates both schools. The twelve students at the BNL program are enrolled in the State University of New York at Stony Brook (SUNYSB) and receive 3 college credits for the lecture course (CHE-361) and 3 additional credits for the laboratory course (CHE-362). In addition to lectures and laboratories, students tour various nuclear facilities offsite, at BNL, and at SUNYSB. Opportunities are given the students to interact with faculty and scientists within the profession through the Guest Lecture Program. Further details are discussed along with results of student surveys for the years 1999 through 2002. 相似文献
9.
The gas-phase thermal isomerizations at 315 °C of cis,anti,cis-tricyclo[6.4.0.02,7]dodec-3-ene to trans-tricyclo[6.2.2.02,7]dodec-9-ene and to cis,endo-tricyclo[6.2.2.02,7]dodec-9-ene favor the former, the more geometrically strained product, by a ratio of 2.4:1. These products correspond to suprafacial inversion (si) and suprafacial retention (sr) stereochemical outcomes. The reaction stereochemistry shown by the 11-carbon homolog, cis,anti,cis-tricyclo[6.3.0.02,7]undec-3-ene, is strikingly different: the [1,3] carbon shift takes place to give only the ‘forbidden’ sr product. Two related bicyclic vinylcyclobutanes, 8-deuterio- and 8-exo-methylbicyclo[4.2.0]oct-2-enes, evidence contrasting reaction stereochemical predilections in [1,3] shifts, but the 12-carbon tricyclic system and the 8-exo-methyl bicyclic analog isomerize with the same si:sr ratio! These observations prompt fresh considerations of structural influences on conformational preferences available to the alkyl, allyl diradical reactive intermediates involved. 相似文献
10.
Rick L. Paul W. Clay Davis Lee Yu Karen E. Murphy William F. Guthrie Dennis D. Leber Colleen E. Bryan Thomas W. Vetter Gulchekhra Shakirova Graylin Mitchell David J. Kyle Jeffery M. Jarrett Kathleen L. Caldwell Robert L. Jones Steven Eckdahl Michelle Wermers Melissa Maras C. D. Palmer M. F. Verostek C. M. Geraghty Amy J. Steuerwald Patrick J. Parsons 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1555-1563
Radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in standard reference material (SRM) 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1 × 1014 cm?2 s?1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix either by retention on hydrated manganese dioxide (urine) or by extraction into zinc diethyldithiocarbamate in chloroform (blood). 76As was quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a 77As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma-mass spectrometry values from National Institute of Standards and Technology and collaborating laboratories to provide certified values of 10.81 ± 0.54 and 213.1 ± 0.73 μg/L for SRM 2668 Levels I and II, and certified values of 21.66 ± 0.73, 52.7 ± 1.1, and 78.8 ± 4.9 μg/L for SRM 955c Levels II–IV, respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level I, an information value of <5 μg/L was assigned for this material. 相似文献