▁School ▁fac ulty ▁Category : B ard ▁College ▁fac ulty ▁Category : De ath s ▁from ▁lung ▁cancer ▁Category : É cole ▁Norm ale ▁de ▁Mus ique ▁de ▁Paris ▁al umn i ▁Category : J ew ish ▁American ▁classical ▁mus icians ▁Category : J ew ish ▁classical ▁mus icians ▁Category : J ew ish ▁American ▁classical ▁compos ers ▁Category : Mus icians ▁from ▁Philadelphia ▁Category : P ul itzer ▁Prize ▁for ▁Music ▁w inners ▁Category : P up ils ▁of ▁A aron ▁Cop land ▁Category : Symbol s ▁of ▁Connecticut ▁Category : 2 0 th - century ▁American ▁compos ers <0x0A> </s> ▁Ph oto ac ids ▁are ▁mole cules ▁which ▁become ▁more ▁acid ic ▁upon ▁absor ption ▁of ▁light . ▁This ▁is ▁due ▁either ▁to ▁the ▁formation ▁of ▁strong ▁ac ids ▁upon ▁phot od is soci ation , ▁or ▁to ▁the ▁dis soci ation ▁of ▁pro tons ▁upon ▁photo associ ation ▁( e . g . ▁ring - clos ing ). ▁ ▁There ▁are ▁two ▁main ▁types ▁of ▁mole cules ▁that ▁release ▁pro tons ▁upon ▁ill um ination : ▁photo ac id ▁gener ators ▁( PA G s ) ▁and ▁photo ac ids ▁( PA H s ). ▁P AG s ▁under go ▁pro ton ▁phot od is soci ation ▁irre vers ibly , ▁while ▁PA H s ▁are ▁mole cules ▁that ▁under go ▁pro ton ▁phot od is soci ation ▁and ▁thermal ▁re associ ation . ▁In ▁this ▁case ▁the ▁excited ▁state ▁is ▁strongly ▁acid ic , ▁but ▁revers ible . ▁