~4) CC/NUMBER 34 ,_ This Week’s Citation Classic ® AUGUST 26. 1991 Cherenkov PA. Visible light from clear liquids under the action of gamma radiation. C.R. (DokI.) Acad. Sci. URSS 2:451-4, 1934. [Phyaico-Mathematicat Institute V.A. Stekiova. Academy of Science. Leningrad. USSRI This paper reports observations of previously un- action of gamma radiation. He observed, as re- known properties ofvisible radiation produced in ported in the 1934 “discovery” paper, that clear liquids under the action of fast electrons, gamma radiation creates a weak luminescence such as beta-particles from radioactive elements of the solution, which differs sharply from nor- or Compton electrons liberated in liquids in the mal luminescence. This observation stimulated processof scatteringof gamma rays. These proper- his extensive further experiments, eventually de- ties include the polarization of the radiation and fining the Cherenkov (or Cherenkov-Vavilov) ef- the marked asymmetry of its emission directional- fect and what we now know as Cherenkov ity. IThe Sd® indicates that this paper has been radiation. cited in more than 100 publications from 1945 to This radiation, seen but not explained by 1990.1 Marie Curie around the turn of the century, is the beautiful blue glow we see in the liquid Faster Than a Speeding Photon surroundingstrong gamma-ray or charged-parti- de emitters such as fuel rods in a swimmingpool John H. Hubbell reactor. This 100 percent polarized light, emit- National Institute of Standards and Technology ted atan angle related by a simple formula to the Gaithersburg, MD 20899 particle velocity and the refractive index of the medium, is produced when energetic partldes, It is an undue honor, but a pleasure nonethe- such as Compton electrons, exceed the velocity less, that I should be invited to write this corn- of light, which is slowed in the dear liquid (or mental)’. This material is based on: (a) a delight- glass, or plastic, etc) in proportion to the recip- fail surprise visit (I thought he was already long rocal of the refractiveindex. deceased) with PA. Cherenkov in his laboratory A sound theoretical basis for the new radia- m Troitsk (just south of Moscow) in 1979; (b) his tion, asan electrodynamical analog to the Mach personal reminiscences recounted in a historical waves of hydrodynamics,2 was provided by I.M. review paper’ he presented at a seminar, Frank and I.E. Tamm and quantitatively34verified “Cherenkov Detectors and Their Applications in by Cherenkov’s further experiments. How. Science and Technics,” celebrating the 50th an- ever, although the work was greeted enthusiasti- niversary of the Vavilov-Cherenkov radiation cally by physics luminary Niels Bohr, Che- discovery; and (C) additional information sup- renkov’s English-language manuscript, “Visible plied to me by one of Cherenkov’s colleagues, radiation produced by electrons moving in a Boris B. Govorkov, RN. Lebedev Institute, who medium with velocities exceeding that of light,” hosted me in Moscow in 1979. was rejected by Nature, whose editors did not Pavel Alekseevicti Cherenkov, who died ofyel- take the work seriously. The Physical Review low jaundice January 6, 1990, in Moscow, was was somewhat more open-minded andaccepted born to a peasant family on July 28, 1904, in the paper, which underwent only a change of Voronezh, a city midway between Moscow and mailing envelope, as a letter to the editor.~ Rostov, on the Voronezh River, just before it In 1958, Cherenkov, Frank, and Tamm shared flows into the Don. A graduate of Voronezh the Nobel Prize in physics “for the discovery and University, he did postgraduate work at the explanation of the Cherenkov effect.” Che- Physics Institute of the USSR Academy of Sci- renkov’s numerous other awards and honors In- ences, Moscow, from 1930 to 1935, from which dude the Order of Lenin (twice) and the State he was awarded a doctorate in natural science in Prize ofthe Soviet Union (threetimes). Although 1940. he was not of great physical stature, Pavel Al- During this period, under the guidance of S.I. ekseevich Cherenkov casts a long shadow (or Vavilov, Cherenkov investigated the lumines- light, actually) across both the history and future cence of solutions of uranium salts under the of radiation physics. I. Cherenkov PA. At the threshold of discovery. NacI. Instrunt. Merit. Phys. Ret. A 248(I): 1-4, 1986. 2. Frank I M& Tamm I E. Coherent visible radiation of fast electrons passing through matter. CR. (Dokla4y) Acod. Sc, IJRSS 14:109-14, 1937. (Cited 55 times since 1945.) 3. Cherenkov PA. Visible light of pure liquids under the action of hard beta-radiation. CR. (Dokiady)Acod. Sci. URSS 14:101-5. 1937. 4. - Angular dependence of the intensity of light emission, produced by gamma-radiation inpure liquids. CR. (Dokl.ody)Acad. Sci. URSS 14:105-8, 1937. 5. Visible radiation produced by electrons moving ina me”ium with velocities exceeding that of light. Phys. Rev. 52:378-9. 1937. Received March 4. 1991 10 ©1991 by ISI® CURRENT CONTENTS®.