ABSTRACT
Atoms and molecules have quantized electronic, rotational, and vibrational energy states. Depending upon the characteristic energy of what needs to be identified, different types of spectroscopy are used. The excitation spectrum varies the excitation wavelength in designated increments and holds the emission monochromator at a specified point. The emission spectrum holds the excitation wavelength fixed and varies the emission filter. The properties of the light source, monochromators, and PMTs are more important for fluorescence than for absorbance spectroscopy. That is because for the latter, a blank sample can be used to correct for inhomogeneities in the transmitted light. As spectrofluorometers are costly, most laboratories have only one, and making the right choice for the desired experiments is important. As with absorption, using samples that are too concentrated is an important source of error. Too high of a concentration leads to scattering and a reduction in signal.
