  We measured X-band electron-spin resonance of single crystalline sodium
vanadate doped with lithium, Na_{1-x}Li_xV_2O_5 for 0 < x < 1.3% . The phase
transition into a dimerized phase that is observed at 34 K in the undoped
compound, was found to be strongly suppressed upon doping with lithium. The
spin susceptibility was analyzed to determine the transition temperature and
the energy gap with respect to the lithium content. The transition temperature
Tsp is suppressed following a square dependence of the lithium concentration
while the energy gap is found to decrease linearly. At high temperatures
(T>Tsp) the susceptibility remains nearly independent of doping.
