The techniques developed at NIST for fabricating alkali atom vapor cells and highly miniaturized atomic frequency references can be used to construct atomic clocks with a wide range of characteristics. Some of these are summarized below:

Atoms: 87Rb, 85Rb and Cs, 39K, and most other elements that do not react chemically with, or diffuse through, glass or Si.

Buffer gases: most noble gases including He, Ne, Ar, Kr, Xe, and other molecular gases such as N2, H2

Buffer-gas pressures: from below 100 Pa to several hundred kPa

Cell sizes: interior dimensions from a few tens of micrometers to several millimeters

Complicated structures such as those shown below, which may include channels and reservoirs.