▁handling ▁of ▁mic row ave ▁radiation . ▁At ▁first ▁they ▁tried ▁to ▁detect ▁the ▁absor ption ▁in ▁long ▁lengths ▁of ▁wave guide , ▁but ▁shortly ▁there after ▁St ark ▁mod ulation ▁was ▁developed ▁and ▁special ▁wave gu ides ▁containing ▁an ▁electro de ▁allowed ▁for ▁the ▁transmission ▁of ▁mic row aves . ▁ ▁Bak ▁was ▁able ▁to ▁repeat ▁this ▁pione ering ▁achiev ement ▁upon ▁his ▁return ▁to ▁C open hagen ▁where ▁he ▁established ▁a ▁world - ren owned ▁labor atory ▁at ▁the ▁University ▁of ▁C open hagen ' s ▁H . C . ▁ Ø r sted ▁Institute . ▁Over ▁the ▁following ▁years , ▁Bak ' s ▁students ▁and ▁colle agues ▁produced ▁over ▁ 3 0 0 ▁papers ▁and ▁publications ▁containing ▁precise ▁determin ations ▁of ▁mole cular ▁geometry ▁from ▁mic row ave ▁spect ra ▁based ▁on ▁inf ra red ▁spect ro sc opy , ▁Ram an - spect ro sc opy , ▁mic row ave - spect ro sc opy ▁and ▁nuclear ▁magnetic ▁radiation ▁spect ro sc opy . ▁These ▁early ▁measurements ▁and ▁results ▁were ▁supp lement ed ▁by ▁Bak ' s ▁work ▁with ▁quantum ▁chem istry ▁calculations ▁of ▁small ▁mole cular ▁structures . ▁Com b ined , ▁this ▁work ▁formed ▁the ▁foundation ▁for ▁much ▁of ▁our ▁understanding ▁of ▁the ▁field ▁today . ▁Most ▁unus ually ▁within ▁the ▁field ▁of ▁spect ro sc opy , ▁Bak ' s ▁research ▁branch ▁encourag ed ▁- ▁as ▁one ▁of ▁the ▁first ▁in ▁chem istry ▁- ▁the ▁interaction ▁between ▁exper ts ▁from ▁discipl ines ▁as ▁diverse ▁as ▁quantum