  As a part of a study on the variation in the 7Li/6Li ratio, high signal to
noise, high resolution spectroscopy of Li I (6708 Angstroms) and K I (4044
Angstroms) were obtained toward zeta and o Per. The lithium isotope shift is
approximately the same as its fine structure splitting (0.158 Angstroms),
resulting in a blend of the 7Li and 6Li lines. Use of the K I line as a
velocity template allowed a straightforward determination of the lithium
isotopic ratio.
  Our high resolution observations show remarkably disparate isotope ratios:
7Li/6Li = 1 0.6 +/- 2.9 toward zeta Per and 3.6 +/- 0.6 and 1.7 +/- 0.3 toward
o Per. While the results toward zeta Per are consistent with the meteoritic
value, the ratio toward o Per's clouds suggest recent Galactic cosmic ray
spallation. This is the first clear and unambiguous evidence for an
interstellar 7Li/6Li ratio that differs dramatically from the Solar System
value. The low ratio indicates a higher cosmic ray flux toward o Per than
toward zeta Per. A higher flux of cosmic rays toward o Per was suggested
earlier in a study of OH and HD chemistry (Federman, Weber, & Lambert 1996, ApJ
463, 181).
  The total lithium abundances and the K/Li ratio are useful in placing the
7Li/6Li ratio into context. We obtained total lithium abundances of (12.2 +/-
2.2) x 10^(-10) toward zeta Per and (9.8 +/- 3.5) x 10^(-10) toward o Per. The
columns of K I and Li I yielded K/Li ratios that revealed no discernable trend.
Since a Li isotope ratio ~2 toward o Per suggests newly processed lithium, the
comparable total Li abundances and K/Li ratios are unexpected.
