AHSTUACTS OF TKCIIXK AL AUTICLKS 407 



ing the presence of some donor-type impurities in addition to the usual acceptor 

 type. The energy (hfference between the acceptors and the fdled l)and is 0.3 

 electron volt, and the total numl)er of impurity atoms is al)out 10" to 10"'' i)er 

 cm^, the number of donors being less than but of the same ordei' as the numl)er of 

 acceptors. One finds that the density of ion chaige in the rectifying layer is of 

 the same order of magnitude as the difference between the donors and acceptors 

 found from the conductivity. The field at the copper-cuprous oxide interface is 

 about 2 x 10^ volts/cm; the height of the potential at the surface as compared 

 with the oxide interior is about 0.5 volt; and the thickness of the space charge 

 la^'er about 5.0 x 10~* cm. The diffusion equation for flow of current through this 

 space charge region can be integrated to give the current in terms of tlie field 

 at the interface and the applied potential across the space charge layer. Two 

 currents are involved, one from the .semi-conductor to the metal (/,) and one 

 from the metal to the semiconductor (/,„) which is similar to a thermionic emis- 

 sion curient into the semiconductor. The net current is, of course, / = /,„ — I>. 

 One can get this "emission" current (/„.) by dividing the true current by the 

 factor 1 - exp { — eVa/kT), where Va is the applied potential. This emission current 

 depends on the absolute temperature and on the field at the copper-cuprous 

 oxide interface. At high fields the logarithm of the current is proportional to the 

 square root of the field, and at low fields the current decreases more rapidly 

 indicating a i)atchy surface having small areas of low potential maximum from 

 which all the emission comes when the field is large. 



Effect of Packaging on Corrosion of Zinc Plated Equipment. K. G. 

 C'ompton\ S. M. Arnold^ and A. Mendizza . Corrosion, 7, pp. 365- 

 372, Nov., 1951. 



Physics as a Science and an Art. K. K. Darrow\ Phys. Today, 4, pp. 

 6-11, Nov., 1951. (Monograph 1914). 



The last of six invited papers presented on October 25th during the symposium 

 on "physics todaj'" which keynoted the 20th Anniver-sar}- Meeting of the 

 American Institute of Physics in Chicago. 



Ionization hy Electron Impact in CO, N2, NO, and O2. H. D. Hagstrum . 

 Revs. Modern Phys., 23, pp. 185-203, July, 1951. (Monograph 1916). 



Ionization b}' electron impact in diatomic gases has- been studied in this work 

 with a mass spectrometer designed to measure 7ti/e, appearance potential, and 

 initial kinetic energy for each ion observed. Results have been obtained for the 

 gases CO, N2 NO, and O2 with some confirmatory work in H2. Discussion is 

 included of the nature and identification of dissociative ionization processes and 

 of the retarding potential and appearance potential measurements. Values of 

 important quantities such as the dissociation energies of CO, N2 , and NO; the 

 sublimation energy of C ; the electron affinity of ; and the excitation energy of 

 0~ are determined again by electron impact in this work. 



> B. T. L. 



