Preparation
aiid
nt .llatcrictl.s. RJ- GORTOSI! F O S I J.\SI> .~ John IYiley a n d Sons. Iri,:.. 194s.
C‘iluracterist (E//ih,
. Tori;:
FREI)ERI(.K SElTZ
Price: S5.00. Twrnty-nine lectuirs :ind tlieii. tliscussion pivrn :rt :I Symposium of t h e l)i\.isioii [ j f Electron Optics of t h e .lmerican P1iysic:tl Society held :it (‘oriirll Universit).. O c t o l r i , ‘2426. 1946, :ire published under thr :iuspices of t h e Satioiial Rese:trrli C‘ouncil. T h e interest in this subject h:ts ivxeivctl i,riien.ed stiniu1:it ioii fmni sevt,ixi >t)iii’ecs: fluorescent lighting. t h e use of luminous mat riinls for mi1itni.y purposes during tile ~ a r , theii, use in television. anti t h r contributioiis in t h e field of electronics t o their iiitrrprrt:Ltion.-or, rather should one s a y , continuing efforts in this dirrctioii. .AS o f t e n hnppriis. :ind not:ibly in t lie fieltl of photography, espri~inientand p m c t i c e I I U V C ~ again outrun theory. T h e domiii:tnt experimental facts t o L e es1)l:iined are tlic stor:igc :iiitl rele~iseof energy in t h e bnsic niaterial. t h e phosi)hor, as iiifluciicetl by tenipc1,ature. r;idi:ttion, and conipositioii. T h e pi’esence, u s u d l y in very sni:tll amounts, of substnr:cca cnllrtl nctivators which are chemically unrelated t o t h e principal m:itcri:il of tlie phojplior is one of t h e essentials of a luminous prepwatioii. .Ivigorous seai.cih for new Insic m i t c i i a l s , activators, and mistures of rither or lioth lins given :t rich yield of new phosphors &I ith niany useful properties. n i t h o u t , Iioivel-er, offrririp corwspondiny nen- :ippiuiches t o iuri~k~meiitnl int erpret ation. I t is g e n e i d l y :igi,eed t h a t t h e activ:ttoi. m a y either substitute for ions i i i tiic ci,yst:il lattice or be situated interstitially as :L foi,eign substance. hi either case i: disrortion is produced in t h e surroundiiig electronic field, resulting in t h e “trappiiig” of dispktcrcl electrons which evriitually in11 into positive “holes” or vacancies in t h e crystal lattice with emission of luminescence. Iiiridentnlly, it n-ould seem tlint t h e tacit assumption t h a t the crystalline s t a t e is necessary requires some explanation, in viciv of the fact that some c1:iss;t.s show t h e same phenomena of storing :ind releasing radiative energy in t h e f o m of phosphorescence, :is !\ell as some orgariic subst:tnces i n solution. It is further agreed th:rt t h e r a t e of emission of stored light energy occurs eithc;. uriinioIeculnrlg or bimolcculnrly :ind t h a t t h e l a t t e r mechanism is usu:illy involved iii t h e lougei,time storage. Siiice glass is liquid, its luniincsceiicc was not corisitleretl noi’ t h r nccumulatior; : i i i i l tiischarge of coloi. in ti’unsparent crystals, ~ \ c l li;noi\n t o 1ir rel:ited in mari\. ii?si:tiic.es 1 o luniinescencc ant1 therniol)hospiiorcscerice. For mi ndniir:ible arid compnct sunini:try of t h e present si:itus of this sub yeferret1 t o t h e iiitiduc*toi.y1tvtui.c of Seitz. \vho voicrs full r r d i z a t i o n of t h e very rutliiiieritary nature of tlie t h e o i t t ical yr:tsp of this very conip1ic:itetl sul)jcet. T h e ir;divitlu:il papers present :L m:iss of csperinirntal ni:iteri:il of great interest. cspecinlly t o tl:oic, pi,immi l l - concerned with t h e production :ind usc of luniinous ni:itrt,i:tl. A subject inclrs t o this inipci.t:trit S ~ of T p:tprrs would have i)t,eil of great adv:L:it:tge t o the rendrr.
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