基频fundamentaltune
从v=0的最低振动能级跃迁至v=1的振动能级产生的红外吸收频率称为基频。
Thelowestfrequencyofavibratingsystem.Thespectrumofaperiodicsignalwillconsistofafundamentalcomponentatthereciprocaloftheperiodandpossiblyaseriesofharmonicsofthisfrequency.Thefrequencyisdirectlyrelatedtothephase-locked,rotationalspeedbeingmeasuredanditsamplitudemaybelowenoughthatitisdifficulttoseeinthespectrum(oritmaybemissingaltogether).Thespectrumofaperiodicsignalwillconsistofafundamentalcomponentatthereciprocalofitsperiodandaseriesofharmonicsofthisfrequency.Thefundamentalisalsocalledthe“firstharmonic”.Evenifthefundamentalissolowinlevelthatitcannotbeseen,theharmonicswillstillbespacedapartbythefundamentalfrequency.