Measurement of isotope shifts in Sm I by using sub-Doppler optogalvanic spectra with a single-frequency semiconductor master-oscillator power-amplifier laser

High-resolution optogalvanic spectroscopy near 670 nm was performed on atom ic samarium generated in a hollow cathode discharge. For this experiment, a master-oscillator power-amplifier semiconductor diode laser source with a nominal output power of 500 mW was constructed. The isotope shifts were mea sured in sub-Doppler atomic spectra for two transitions: one at 667.151 nm (4f(6)6s(2) E-7(6) - 4f(6)6s6p F-9(7)) and the other at 672.588 nm (4f(6)6s (2) F-7(0) - 4f(6)6s6p F-9(1)). We showed that the field shifts estimated f rom the King plots contributed mainly to the observed isotope shifts for bo th transitions. Changes in the mean-square nuclear charge radii were derive d from the field shifts. The output characteristics of a semiconductor powe r-amplifier with a laterally tapered gain region and seeded by a grating-tu ned external-cavity diode laser are also reported.