  This article presents spectroscopy results of the $5s5p{\;^3}P_0 \rightarrow
5s5d{\;^3}D_1$ transition in all isotopes of laser cooled Sr atoms and the
utility of this transition for repumping application. By employing the
$5s5p{\;^{3} P_{0}} \rightarrow 5s5d{\;^3}D_1 $ (483 nm) transition in
combination with the excitation of $5s5p{\;^3}P_2 \rightarrow 5s6s{\;^3}S_1$
(707 nm) transition, we observe a significant increase ($\sim$ 13 fold) in the
steady state number of atoms in the magneto-optic trap (MOT). This enhancement
is attributed to the efficient repumping of Sr atoms that have decayed into the
dark $5s5p{\;^3}P_2$ state by returning them to the ground state
$5s^2{\;^1}S_0$ without any loss into the other states. The absolute transition
frequencies were measured with an absolute accuracy of 30 MHz. To support our
measurements, we performed Fock-space relativistic coupled-cluster calculations
of the relevant parameters in Sr. To further increase the accuracy of the
calculated properties, corrections from the Breit, QED and perturbative triples
were also included. The calculated branching ratio for the repumping state
confirms the significantly increased population in the ${^3}P_1$ state.
Thereby, leading to an increase of population of atoms trapped due to the
enhanced repumping. Our calculated hyperfine-splitting energies are in
excellent agreement with the measured values. Moreover, our calculated isotope
shifts in the transition frequencies are in good agreement with our measured
values.
