Mercury depletion as a way of changing the emission spectrum of a fluorescent lamp

We present a promising option for changing the emission spectrum of a fluor escent lamp. In a neon/mercury discharge, neon radiation is produced when t he mercury density is sufficiently low. Under certain discharge conditions, radial cathaphoresis causes depletion of mercury atoms in the center of th e plasma. This effect is especially well pronounced at high electrical curr ents and low mercury pressures. We measured the color temperature of a fluo rescent lamp containing a neon/mercury discharge at several mercury pressur es and currents. The color temperature of this lamp varied from 4000 to 210 0 K. We also performed ultraviolet absorption measurements. From these meas urements, we obtained the mercury atom density profile in the discharge. A significant decrease of the mercury density in the center of the plasma is indeed observed under certain discharge conditions. (C) 2000 American Insti tute of Physics. [S0003-6951(00)00612-4].