A concise overview of diode-laser applications in the spectroscopy of
intercombination transitions of alkaline-earth atoms that were carried
out by several groups is presented. The properties of the intercombin
ation lines of Ba, Sr, Ca, and Mg are discussed in connection with the
ir possible use in metrology. The set of these lines is compared with
the set of resonant lines of alkalines. Available techniques for the p
reparation of adequate atomic ensembles and diode-laser systems provid
ing high resolution are discussed. We report also on the new results o
btained for the intercombination line of strontium: a saturated absorp
tion resonance of the 5(1)S(0)-5(3)P(1) transition in Sr has been obse
rved in an atomic beam with a highly coherent diode laser. The minimum
line width of the nonlinear resonance is 200 +/- 20 kHz. The isotope
shifts corresponding to Sr-86 and the F = 9/2 --> F' = 7/2 hyperfine c
omponents of Sr-87 measured with respect to the Sr-88 isotope to be 15
5 +/- 5 and 206 +/- 5 MHz, respectively.