In this experimental work, we report our findings about a transition between states of even parity 5S1/2 → 5D5/2 of Rb atoms under different conditions of transit time broadening. For this purpose, the blue fluorescence emanating from the associated decay 5D5/2 → 6P3/2 → 5S1/2 channel is monitored. Based on the relative magnification of the laser beam, which is used in excitation between levels of even parity, the system exhibits two photon absorption (TPA) through blue fluorescence peaks. The TPA profile appears as a Lorentzian peak on a Doppler background. The change in the laser beam diameter directly influences the relative contributions of Lorentzian and Doppler parts. A direct inference drawn from of this study may be utilized in optimizing the extraction of the first derivative spectrum corresponding to 5S → 5D transitions.