  We present measurements of the \ion{K}{i} $\lambda 7699$ line from spectra of
19 late-type members of the $\alpha$Persei cluster obtained with the
Intermediate Dispersion Spectrograph at the Isaac Newton Telescope. These stars
span a narrow range of $T_\mathrm{eff}$, from 5091 K to 4771 K, and a wide
range of $v \sin i$ values (9 $\mathrm{km s}^{-1}$--170 $\mathrm{km s}^{-1}$).
We find empirically that larger rotational broadening increases the equivalent
width of \ion{K}{i} $\lambda 7699$ linearly for $v \sin i$ values from 15
$\mathrm{km s}^{-1}$ to 75 $\mathrm{km s}^{-1}$. This correlation breaks down
for $v \sin i >$ 75 $\mathrm{km s}^{-1}$. After correction for this effect, we
show that the potassium line equivalent widths do not correlate with $v \sin
i$.}
