Question

(10 points) Describe the basic design difference between a spectrometer for absorption measurements and one for emission studies. Sketch a stylized diagram of each.

Answer 1

The one that is used for absorption measurement is called Spectrophotometer and the one used for emission studies is called as Spectrofluorometer.

Spectrophotometer:

The term spectrophotometer is used specifically to refer to a spectrometer which measures the absorption of light by a sample.

It comprises a white light source typically deutrium arc lamp to cover UV range and a tungsten lamp to cover visible. Thie system is also equiped with an excitation monochromator which selects the wavelength of light that reaches the sample. This light is ttransmitted through the sample (in solutions). The intensity of the transmitted monitored using a detector which is typically a photomultiplier tube or silicon photodiode. The output comes as a UV-Vis spectrum

Photo multiple tube TON Sowne Excitation Monochromatis

Spectrofluorometer

The excitation side of a spectrofluorometer is equivalent to the spectrophotometer: a white light source and an excitation monochromator. Xenon arc lamps are used as the light source.The sample is illuminated by the chosen excitation wavelength which causes it to fluoresce. The fluorescence emission is collected by the emission monochromator which is orientated at 90 degrees to the excitation monochromator and the selected wavelength reaches the detector; typically a photomultiplier tube

Lught Source Ercitation prono chromato Emission monochromates Ext slit fude

Answer 2

An absorption spectrometer requires a separate radiation source and a sample compartment that holds containers for the sample and blank. With an emission spectrometer, the sample is introduced directly into a hot plasma or flame where excitation and emission occur