Question

In Laser Opto-acoustic spectroscopy, the IR beam excites the molecules to higher states. In which of the following ways do the molecules return to the ground state?

(a) Collisional de-excitation

(b) Random de-excitation

(c) By spontaneous emission

(d) By stimulated emission

This question was posed to me by my college professor while I was bunking the class.

The origin of the question is NO2 Analyser in chapter Industrial Gas Analysers of Analytical Instrumentation

Answer 1

The correct choice is (a) Collisional de-excitation

For explanation I would say: The molecules return to the ground state by collisional de-excitation. This results in an increase in temperature.