raracah parameterracemicracemizationradialradial probability densityradial probability distributionradial quantum numberradianradiationradiation energyradicalradical inhitatorradical intiatorradical ion polymerizationradioactiveradioactive decayradioactivityradiochemistryradioisotoperadiologyradiolysisradiometryradiumradius of gyrationradonraffinaterandie branching indexrandomrandom copolymerrandom distributionrangerankine temperature scalerapid flowrare earthsrare gasrasching synthesisraterate constantrate determining steprate equationrate of dissolutionrate of reactionratiorational numberrayrayleigh jeans lawrbrereactant