▁study ▁nan ometer ▁s ized ▁differences ▁in ▁structure . ▁ ▁At omic ▁scatter ing ▁factors ▁ ▁In ▁X - ray ▁diff raction ▁the ▁scatter ing ▁factor ▁f ▁for ▁an ▁atom ▁is ▁roughly ▁proportional ▁to ▁the ▁number ▁of ▁electrons ▁that ▁it ▁poss esses . ▁However , ▁for ▁w avel ength s ▁that ▁approximate ▁those ▁for ▁which ▁the ▁atom ▁strongly ▁absor bs ▁radiation ▁the ▁scatter ing ▁factor ▁under go es ▁a ▁change ▁due ▁to ▁anom alous ▁disp ersion . ▁The ▁disp ersion ▁not ▁only ▁affect s ▁the ▁magnitude ▁of ▁the ▁factor ▁but ▁also ▁im parts ▁a ▁phase ▁shift ▁in ▁the ▁el astic ▁collision ▁of ▁the ▁phot on . ▁The ▁scatter ing ▁factor ▁can ▁therefore ▁best ▁be ▁described ▁as ▁a ▁complex ▁number ▁ ▁f = ▁fo ▁+ ▁ Δ f ' ▁+ ▁i . Δ f " ▁ ▁Con tr ast ▁variation ▁ ▁The ▁anom alous ▁aspects ▁of ▁X - ray ▁scatter ing ▁have ▁become ▁the ▁focus ▁of ▁considerable ▁interest ▁in ▁the ▁scientific ▁community ▁because ▁of ▁the ▁avail ability ▁of ▁syn ch ro tr on ▁radiation . ▁In ▁contrast ▁to ▁desktop ▁X - ray ▁sources ▁that ▁work ▁at ▁a ▁limited ▁set ▁of ▁fixed ▁w avel ength s , ▁syn ch ro tr on ▁radiation ▁is ▁generated ▁by ▁acceler ating ▁electrons ▁and ▁using ▁an ▁und ulator ▁( device ▁of ▁periodic ▁placed ▁di pole ▁magnet s ) ▁to ▁" wig gle " ▁the ▁electrons ▁in ▁their ▁path , ▁to ▁generate ▁the ▁wanted ▁w avel ength ▁of ▁X - ray s . ▁This ▁allows ▁scient ists ▁to ▁vary ▁the