简介：Intramolecularvibrationsoflargemacromoleculesresideintheterahertzrange.Inparticular,proteinvibrationsarecloselyspacedinfrequency,resultinginanearlycontinuousvibrationaldensityofstates.Thisdensityofvibrationsinterfereswiththeidentificationofspecificabsorptionlinesandtheirsubsequentassociationwithspecificfunctionalmotions.Thischallengeiscompoundedwiththeabsorptionbeingdominatedbythesolventandlocalrelaxationalmotions.Astrategyforremovingtheisotropicrelaxationallossandisolatingspecificvibrationsistousealignedsamplesandpolarization-sensitivemeasurements.Here,wedemonstrateatechniquetorapidlyattaintheanisotropicresonantabsorbanceusingterahertztimedomainspectroscopyandaspinningsample.Thetechnique,modulatedorientation-sensitiveterahertzspectroscopy(MOSTS),hasanonzerosignalonlyforanisotropicsamples,asdemonstratedbyacomparisonbetweenasiliconwaferandawiregridpolarizer.Forsucroseandoxalicacidmolecularcrystals,theMOSTSresponseisinagreementwithmodeledresultsfortheintermolecularvibrations.Further,wedemonstratethat,eveninthepresenceofalargerelaxationalbackground,MOSTSisolatesunderlyingvibrationalresonances.