Knowledge Bank

We discuss some general considerations for obtaining, independently of any information on molecular concentration, absolute intensity determinations from relative molecule. This new method exploits the effect, first elucidated sixty years $ago1$, which vibration-rotation interaction has on relative rovibrational line intensities in a vibrational band. This approach is important for vibrational fundamental bands of diatomic molecules since they cannot be studies by the lifetime method which requires the radiative relaxation lifetime to be much shorter than competing collisional relaxation processes. Our new method should be particularly significant for diatomic radical species whose concentrations can be inferred only indirectly.