neutronn.

1899 W. Sutherland in London, Edinb., & Dublin Philos. Mag. 5th Ser. 47 273 If the electrons are distributed through the æther, we must suppose that in æther showing no electric charge each negative electron is united with a positive electron to form the analogue of a material molecule, which might conveniently be called a neutron.

1912 E. M. Wellisch & H. L. Bronson in Amer. Jrnl. Sci. 33 497 On this view there must be present in the gas certain molecules, or neutrons, which are in a condition allowing of relatively easy ionization.

1921 W. D. Harkins in London, Edinb., & Dublin Philos. Mag. 6th Ser. 42 309 Any complex atom has a mass and weight 0·76 per cent. less than the hydrogen atoms (neutrons) from which it may be assumed to be built.

1921 W. D. Harkins in London, Edinb., & Dublin Philos. Mag. 6th Ser. 42 315 The term neutron represents one proton plus one electron.

1921 J. L. Glasson in London, Edinb., & Dublin Philos. Mag. 6th Ser. 42 597 In the ordinary atom of hydrogen we have a single electron separated from the nucleus by a distance of the order of 10⁻⁸ cm. It is here contemplated that a more intimate union of the two is possible... Such a particle, to which the name neutron has been given by Prof. Rutherford, would have novel and important properties. It would, for instance, greatly simplify our ideas as to how the nuclei of the heavy elements are built up.

1930 E. Rutherford et al. Radiations from Radioactive Substances xvii. 523 The existence of a neutron, i.e. a close combination of a proton and electron, has been suggested.

1932 J. Chadwick in Nature 27 Feb. 312/1 These results..are very difficult to explain on the assumption that the radiation from beryllium is a quantum radiation, if energy and momentum are to be conserved in the collisions. The difficulties disappear, however, if it be assumed that the radiation consists of particles of mass 1 and charge 0, or neutrons. The capture of the α-particle by the Be⁹ nucleus may be supposed to result in the formation of a C¹² nucleus and the emission of the neutron.

1938 R. W. Lawson tr. G. von Hevesy & F. A. Paneth Man. Radioactivity (ed. 2) ix. 94 We must regard these protons and neutrons as the ultimate constituents of the nuclei, and consider the α-particle as a kind of ‘molecule’ of the ‘nuclear atoms’ possessing especial stability, and arising from the union of 2 protons and 2 neutrons.

1951 S. Dushman Fund. Atomic Physics xiii. 227 The U-235 nucleus, in splitting, emits high-speed neutrons which may produce fission in other U-235 nuclei, thus initiating a chain reaction.

1968 M. S. Livingston Particle Physics ii. 25 The nucleus could now be conceived as a closely packed assemblage of protons and neutrons, with the atomic charge number Z given by the number of protons and the atomic weight number A by the total of protons and neutrons.

1972 Physics Bull. June 349/1 Although it is comforting and often convenient to consider the proton and neutron as elementary particles with no internal substructure, they are in fact particles in a state of continual change.

1973 A. J. MacLeod Instrumental Methods Food Anal. vii. 684 Isotopes of an element possess different numbers of neutrons in their nuclei, but are otherwise identical.

1989 C. Caufield Multiple Exposures (1990) vi. 44 As heavy as a proton, but without an electrical charge, the neutron was the perfect bombardment tool, able to fly into the nucleus of an atom and break it apart.

2000 Sciences May 18/2 Today's so-called standard model describes the neutron as a composite particle—not made up of an electron and a proton..but of one up quark and two down quarks.

1941 Proc. Royal Soc. A. 178 479 No appreciable deuteron-activation of the collector should remain after the lapse of this time, and the small ‘background’ observed..is attributed to neutron-activation.

1965 D. Gibbons in J. M. A. Lenihan & S. J. Thomson Activation Anal. x. 68 Phosphorus and barium can be determined..using 14 MeV neutron activation and γ-ray spectrometry.

1990 Jrnl. Petrol. 31 1383 The samples..were analysed..for trace elements by energy-dispersive X-ray fluorescence and instrumental neutron activation procedures.

1947 Jrnl. Amer. Chem. Soc. 69 2810/1 (caption) Neutron activation analysis of spectrographically pure erbium oxide.

1987 London Archaeologist Winter 340/2 Problems of fabric attribution are being met by a programme of neutron activation analysis at the British Museum Research Laboratory.

1960 Congress. Rec. 12 May 10138/3 Although there have been a few fragmentary references to the neutron bomb in the press, I was told..that the matter was classified.

1962 L. Deighton Ipcress File xxiv. 155 I guessed that it was a neutron bomb that they were about to explode.

1977 Whig-Standard (Kingston, Ont.) 8 July 1/1 The Defence Department plans to deploy in Europe within the next 18 months the so-called neutron bomb, a tactical weapon designed to kill enemy troops with radiation.

1985 D. Lucie Hard Feelings i. iii, in Progress & Hard Feelings 59/2 This cocktail is my very own invention. The Neutron Bomb. Destroys human flesh, but leaves the house intact.

1996 Wired May 150/3 Reengineering is like hitting a company with a neutron bomb: the buildings are still standing, but the people are gone.

1936 Science 22 May 481/2 Radio-iridium probably is the product in a reaction in which the deuteron is captured by the platinum nucleus and an alpha particle is emitted. On the other hand, the production of radio-platinum involves only neutron capture.

1936 Chem. Rev. 18 485 Two neutron-capture reactions have been known for bromine for some time.

1966 C. S. G. Phillips & R. J. P. Williams Inorg. Chem. II. xxxv. 635 Neutron-capture efficiencies are usually measured in terms of nuclear cross-sections, for which the whimsical unit the ‘barn’ has been devised.

1994 H. Karttunen et al. Fund. Astron. (ed. 2) xi. 270 Elements heavier than iron are almost exclusively produced by neutron capture during the final violent stages of stellar evolution.

1954 Amer. Jrnl. Roentgenol., Radium Ther. & Nuclear Med. 71 280/1 The development of procedures to achieve neutron capture therapy was among the first projects of the Medical Department [at Brookhaven].

1990 Sci. Amer. Oct. 68/1 The possibility that progress toward another powerful therapy might be made has led the authors..to work on an approach called boron neutron capture therapy.

2000 Radiation Res. 154 556 Some recent neutron capture therapy research has focused on using compounds containing the element gadolinium.

1950 S. Glasstone Sourcebk. Atomic Energy xi. 306/2 Three main techniques have been developed for making measurements with neutrons of specific energies; these are the time-of-flight velocity selector..; the mechanical selector, sometimes referred to colloquially as a ‘neutron chopper’..; and the crystal spectrometer.

1996 Rev. Sci. Instruments 67 2770 A very small Fermi-type neutron chopper fashioned by cutting slots in a boron nitride cylinder was developed for use with a source of thermal and cold..neutrons.

1941 Proc. Royal Soc. A. 178 484 The emission of ‘delayed’ neutrons has been sought with the help of a neutron counter consisting of a 2mm. deep pulse-recording ionization chamber with a surface bearing a film of paraffin wax.

1961 G. R. Choppin Exper. Nucl. Chem. viii. 117 Most neutron counters use detectors which contain BF₃ gas usually enriched in B¹⁰.

1998 Wired Nov. 223/1 The neutron counter was very sensitive. Any time anyone in Prague turned on a big machine, the counter counted it.

1948 Science 2 July 69 The new field of neutron diffraction..promises to be a useful partner to the above fields in molecular and crystal structure studies.

1973 J. Yarwood Atomic & Nucl. Physics xiii. 381 Whereas X-ray diffraction cannot readily lead to a knowledge of the positions of hydrogen atoms in a crystal because the scattering is dependent on the number of orbital electrons.., neutrons are strongly scattered by hydrogen nuclei. The technique of neutron diffraction therefore supplements that of X-ray diffraction.

1941 Proc. Royal Soc. A. 178 483 Owing to their neutron excess the fragment nuclei would be expected to have α-particle binding energies greater even than those of neighbouring isotopes that are known to be α-stable.

1992 Philos. Trans. (Royal Soc.) A. 341 17 Conditions in neutron stars are more extreme than almost any encountered on Earth: densities exceed those of atomic nuclei, and matter has a large neutron excess.

1947 Sci. Monthly Mar. 215/2 This difference in neutron number makes possible various methods of analysis for the different isotopes.

1955 R. D. Evans Atomic Nucleus iii. 99 Nuclei having the same neutron number are isotones.

2000 Nature 30 Mar. 447/1 Both the proton number (28) and the neutron number (20) of nickel-48 correspond to full shells, called ‘magic’ numbers by nuclear physicists, so nickel-48 is ‘doubly magic’.

1945 H. D. Smyth Gen. Acct. Devel. Atomic Energy Mil. Purposes viii. 84 The high intensity beam of neutrons produced by this pile has been found well-suited to the study of ‘neutron optics’, e.g. reflection and refraction of neutron beams as by graphite.

1994 Thin Solid Films 246 110 (heading) Development of Ni/Ti multilayer supermirrors for neutron optics.

1948 H. Kallmann in Research 1 254/1 The first successful experiments in neutron radiography are due to the author and his collaborator E. Kuhn, who in the years 1935–39 developed and partly tried out the fundamental methods of neutron radiography.

1999 NDT&E Internat. 32 41/2 Contrast agents have been successfully employed in many different applications of neutron radiography.

1949 Science 28 Jan. 82/1 The advantage of the present theory over that of Mayer and Teller is that we are able to account for the neutron-rich heavy nuclei in a natural way.

1961 G. R. Choppin Exper. Nucl. Chem. i. 3 If a nucleus has a high n/p ratio, it is said to be neutron rich. It will be unstable and will decay in a manner that will tend to bring the n/p ratio closer to the stable value.

1998 Proc. National Acad. Sci. U.S.A. 95 19/1 There are considerable uncertainties associated with the nuclear properties of the unstable, neutron-rich progenitors of the uranium and thorium isotopes of interest.

1935 Proc. Royal Soc. A. 150 640 These figures may be taken to be proportional to the nuclear cross-sections for neutron scattering and gamma production respectively.

1974 Physics Bull. Oct. 443/2 The three essential components of a neutron scattering spectrometer: monochromatizing crystal, material sample and crystal for analysis of the scattered beam.

2001 New Scientist 26 May 100/1 (advt.) The work will involve small-angle neutron scattering studies of polymer conformation.

1946 Physical Rev. 70 154/1 This neutron spectrometer system uses the method of arc modulation.

1948 Nucleonics May 167/3 Modified rotating shutter neutron spectrometer.

1994 Science 12 Aug. 859/3 Clementine 2..may yield valuable science, such as an attempt to find moon ice using gamma-ray and neutron spectrometers.

1934 W. Baade & F. Zwicky in Physical Rev. 45 138/2 We advance the view that supernovae represent the transitions from ordinary stars into neutron stars, which in their final stages consist of extremely closely packed neutrons.

1977 Dædalus Fall 45 Pulsars, that is, rotating neutron stars, have been detected in the Crab Nebula and in Vela X, a supernova remnant about ten times older than the Crab Nebula.

1998 New Scientist 2 May 15/1 All known soft gamma repeaters lie within the debris of exploded stars, so scientists suspect the flashes come from neutron stars—the collapsed remains of stellar cores.

1940 Proc. National Acad. Sci. U.S.A. 26 182 This method..removes..the danger of skin burns and similar disturbing factors which are prevalent in x-ray, γ-ray and fast neutron therapy.]

1942 Proc. National Acad. Sci. U.S.A. 28 35 This result is of interest in x-ray and neutron therapy.

1974 Nature 25 Jan. 173/1 Because of Hammersmith Hospital's success in the use of neutron therapy for the treatment of cancer a second British hospital is to be supplied with a compact cyclotron.

1980 Jrnl. Royal Soc. Arts Jan. 96/2 Neutron therapy machines are considerably more expensive than the usual radiotherapy equipment.

2000 Mutation Res. 452 179 The comet assay is a potential tool for use in neutron therapy, as well as a method for the rapid screening of samples from individuals accidentally exposed to radiation.

1977 Washington Post (Nexis) 7 June a5 In April, 1976, according to Pentagon sources, President Ford approved funds to start building the Lance neutron warhead as the first in a new generation of tactical mini-nukes.

1994 Glasgow (Herald) 13 Apr. (heading) Russia may have mini neutron warhead.