The London, Edinburgh and Dublin philosophical magazine and journal of science . was not found possibleto bring an intense source closer tiian 3 cm. from the screenon account of the luminosity excited in it by the <y rays andswift /3 rays, which prevented counting of weak strong magnetic field was necessary to bend away the/3 rays which caused a very marked luminosity on the field of 6000 gauss was generally employed for thispurpose. 544 Sir E. Rutherford on Collision of § 6. Scintillations due to source and absorbing screens. When the containing vessel was exhaust
The London, Edinburgh and Dublin philosophical magazine and journal of science . was not found possibleto bring an intense source closer tiian 3 cm. from the screenon account of the luminosity excited in it by the <y rays andswift /3 rays, which prevented counting of weak strong magnetic field was necessary to bend away the/3 rays which caused a very marked luminosity on the field of 6000 gauss was generally employed for thispurpose. 544 Sir E. Rutherford on Collision of § 6. Scintillations due to source and absorbing screens. When the containing vessel was exhausted of air, scintil-lations were always observed on the screen proportional innumber to the activity of the source. The number fell offrapidly between 7 and 12 cm. air absorption and then moreslowly, but a few could be observed nearly to 28 cm. Thevariation of number with amount of absorption in terms ofcms. of air is shown in fig. 2. This refers to a heated brasssource, 3*3 cm. from the screen, with a heated silver plateof stopping power 6 cm. of air just before the 9 13 17 21 25 /Panye in cms. of a/r These scintillations appear to be due mainly to H atomsexcited partl)T in the source and partly in the absorbing-screens. Thin foils of aluminium, for example, placed closeto the source increase the number of scintillations. This isdue to the occlusion of hydrogen, which can be removed byheating the aluminium in an exhausted furnace just belowthe melting-point. Similar effects were observed with silverb>ut not with gold. In practice, all screens to be usedin the path of the a rays were heated to drive off occludedgases as far as possible. This is very necessary when smallnumbers of scintillations have to be counted. Usually asilver plate was used to absorb the a. rays. Gold was foundto be very free from hydrogen, but it could not be used inplace of silver close to the screen on account of the markedluminosity set up on the screen well beyond the range of thea particle
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
