In an absorption spectroscopy experiment, this absorption is determined as a function of wavelength, frequency or energy in an instrument called spectrophotometer or spectrometer (fig.1.1).
|Fig.1.1 an absorption spectroscopy experiment|
A detector measures the intensity of radiation that passed through the sample unabsorbed; when the intensity of the source through the amount of radiation absorbed by the sample is known.
|Fig.1.2 Infrared Spectrum of nonane|
|Fig.1.3 The UV spectrum of isoprene dissolved in methanol shows Λmax=222nm,ε=20,000|
There are many types of spectroscopy. The three types of greatest use to organic chemist for structure determination are NMR, IR and UV and spectroscopy.
These type of spectroscopy differ conceptual only in the type of radiation used, although the kind of spectrometer required for each are quite different.Mass spectroscopy is fourth physical technique but it is not a type of absorption spectroscopy and thus fundamentally different from NMR ,IR and UV spectroscopy.