The optical piston: A new mechanical action of light

The authors consider a capillary cell which is open instead of closed as in the authors' previous work. The capillary forms the connection between two infinite reservoirs. The whole system is filled with a binary mixture of Na + noble gas, and the optical thickness of the capillary is ≅30. At t = 0 a laser beam is admitted and tuned to the red Doppler wing of the NaD/sub 2/ transition. A steep Na density profile then develops at a specific position along the capillary. After ≅1 min, the profile becomes stationary; a uniform flux of Na flows through the open capillary, driven by LID in the illuminated part and by diffusion in the dark part. For study of LID this stationary behavior in the open-cell regime is attractive since surface effects are less important. Surface effects complicate the dynamics of the optical piston in the closed-cell regime