I. S. Shahin Created 2026-10-18 Updated 2026-11-05
Coauthored saturation spectroscopy of sodium using a pulsed tunable dye laser, resolving hyperfine structure. A delayed probe detected velocity-selective optical pumping, while time-resolved measurements followed collisional redistribution in an argon buffer gas.[ref]
High-Resolution Saturation Spectroscopy of the Sodium D Lines with a Pulsed Tunable Dye Laser by Theodor W. Hänsch and others. Abstract: resolved splittings, delayed-probe hole burning and buffer-gas thermalization
Theodor W. Hänsch, I. S. Shahin and Arthur Leonard Schawlow reported pulsed dye laser saturation spectroscopy of sodium D lines in 1971. They resolved hyperfine structure; delaying the probe revealed persistent changes in ground-level distributions of velocities from optical pumping. Added argon allowed observation of collisional recovery. These measurements probe population memory as well as line positions.[ref]
High-Resolution Saturation Spectroscopy of the Sodium D Lines with a Pulsed Tunable Dye Laser by Theodor W. Hänsch and others. Hänsch, Shahin and Schawlow, 1971, abstract; published September 13
The two-level saturation population model explains depletion in a closed transition; the delayed multilevel optical pumping signal needs additional populations and time dependence. A measured Doppler-free saturation spectroscopy feature can still contain natural linewidth, power broadening, pressure broadening, finite interaction time, imperfect alignment and laser spectral width. The word “Doppler-free” removes a particular thermal broadening mechanism, not every limit on resolution.
Arthur Leonard Schawlow's 1981 recognition concerned laser spectroscopy.[ref] Theodor W. Hänsch received a distinct award in 2005 for precision laser spectroscopy.[ref]
Physik-Nobelpreis 2005 an Theodor W. Hänsch by Max Planck Society. Max Planck Society, October 4, 2005, opening and award explanation