  We have studied modification of the fluorescence spectra of a
room-temperature atomic rubidium vapor in the region of $^{85}$Rb and $^{87}$Rb
D$_2$ line while changing the temporal rate of linear (triangular) scanning of
laser radiation frequency. Increase of the ramping speed over certain value
($\approx$ 10$^6$ MHz/s) results in essential modification of magnitudes of
individual atomic transitions, different on rising and falling slopes, which
characterize transition from a steady-state interaction regime to a transient
one. Our experimental results are well consistent with the developed
theoretical model. The obtained results can be used for determination of atomic
system parameters such as ground-state relaxation rate. Possible follow-up
actions on addressed control of atomic levels population is discussed.
