Full set of Notes with Fill-Ins - San Jose State University

Chem 155 Unit 6 Page 134 of 316But – Echelle monochromators have a strangehandicap. At a given angle β, many wavelengths maysimultaneously be striking the detector!nλ = 2dsin(β)63x300 = 2dsin(β)but…62x??? = 2dsin(β) also!n 1 λ 1 = n 2 λ 2 λ 2 = n 1 λ 1 /n 2n……61 309.8362 304.8463 30064 295.3165 290.77…………λ / nmThis problem is called:Order overlapIs this a problem for Czerny-Turner monochromators?If n 1 =1 and λ 1 =300nm then for n 2 =2, λ 2 = 150 nmIf n 1 =1 and λ 1 =800nm then for n 2 =2, λ 2 = 400 nmCzerny-Turner monochromators handle this problemwith:Order sorting filters – when long λ’s aredesired, short λ’s are absorbed by filtersPage 134 of 316