Question

Compare EELS to conventional IR and Raman spectroscopy. Focus on what is used to excite and detect vibrations. What are the advantages and limitations of EELS?

Short answer

The transmitted infrared radiations are measured after they pass through the sample in infrared spectroscopy. The scattered radiations in the visible region are measured after they pass through the sample in Raman spectroscopy.

Step-by-step solution

Step 1. Explanation

In electron energy-loss spectroscopy (EELS), a beam of electrons having low energy strikers the surface of the sample and excites vibrations. Due to vibrational excitation of the surface molecules, some of the scattered electrons suffer loss in energy. The resultant loss in energy is then detected and related to the vibrations excited.

On the other hand, in infrared spectroscopy, the transmitted infrared radiations are measured after they are passed through the sample. In Raman spectroscopy, the scattered radiations in the visible region are measured after they passed through the sample.

Step 2. Advantages and limitations

The advantage of electron energy-loss spectroscopy ( EELS) is that it provides information regarding the identification and characterization of surface species. On the contrary, conventional IR and Raman spectroscopy is more useful in measuring vibrational modes in a bulk sample.

The limitation of electron energy-loss spectroscopy (EELS) is the low resolution of EELS instruments. The resolution of EELS instruments is greater than$10{\mathrm{cm}}^{-1}$and is low as compared to that of the IR and Raman instruments.