Absolute frequency measurements on the $5s5p^3$P${}_0\to 5s6d^3$D${}_1$ transition in strontium

We report the first absolute frequency measurements for the $5s5p^3$P${}_0\to 5s6d^3$D${}_1$ transition at 394 nm for all the stable strontium isotopes by utilizing repumping induced spectroscopy in a magneto-optical trap. Absolute transition frequency is measured to be 760524409251(25) kHz for ${}^{88}$Sr.With reference to ${}^{88}$Sr, the isotope shifts are measured to be 91052(35), 54600(33), and 51641(28) kHz for ${}^{84}$Sr, ${}^{86}$Sr, and ${}^{87}$Sr, respectively. We calculate the hyperfine constants A and B for the fermionic isotope ${}^{87}$Sr at kHz level. Furthermore, we perform King plot analysis by combining isotope shifts on the 689-nm transition to our data.