Collision broadening and shift of the lithium resonance line by helium

The collision broadening and shift of the lithium resonance line, formed in absorption under low pressures of helium, have been measured. The (half) half-width gamma and shift beta are found to vary with helium density N according to the following relations: gamma /N=(1.73+or-0.10)*10 -9 rads -1 atom -1 cm 3 beta /N=(0.00+or-0.05)*10 -9 rad s -1 atom -1 cm 3 . A recent theoretical calculation is in reasonable agreement with these results.