  Collisions with chemically inert atoms or molecules change the hyperfine
coupling of an alkali-metal atom through the hyperfine-shift interaction. This
interaction is responsible for the pressure shifts of the microwave resonances
of alkali-metal atoms in buffer gases, is an important spin interaction in
alkali-metal--noble-gas van der Waals molecules, and is anticipated to enable
the magnetoassociation of ultracold molecules such as RbSr. An improved
estimate is presented for the long-range asymptote of this interaction for Na,
K, Rb, and Cs. To test the results, the change in hyperfine coupling due to a
static electric field is estimated and reasonable agreement is found.
