DYNAMICALLY MAINTAINED STEADY-STATE PRESSURE-GRADIENTS

In a sealed blackbody cavity with gas, pressure gradients commonly tak e three forms: (a) statistical fluctuations, (b) transients associated with the system relaxing toward equilibrium, and (c) equilibrium pres sure gradients associated with potential gradients (such as with gravi ty). In this paper, it is shown that in the low-density (collisionless ) regime, a fourth type of pressure gradient may arise, this due to st eady-state differential thermal desorption of surface species from che mically active surfaces. This gas phase is inherently nonequilibrium i n character. Numerical simulations using realistic physical parameters support the possibility of this gas phase and indicate that these nov el pressure gradients might be observable in the laboratory; candidate chemical systems are suggested.