  We have completed a new measurement of the Stark shift in 115In within the
410 nm 5P1/2- 6S1/2 transition. We measure the Stark shift constant to be kS= -
122.92(33)kHz/(kV/cm)^2, corresponding to a difference in the 6S1/2 and 5P1/2
state polarizabilities, \Delta\alpha_0, of 1000.2 (2.7) a.u.(in atomic units).
This result is a factor of 30 more precise than previous measurements and is in
excellent agreement with a new theoretical value based on an ab initio
calculation of the wave functions in this three-valence-electron system. The
measurement was performed in an indium atomic beam apparatus, used a GaN laser
diode system, and exploited an FM spectroscopy technique to extract laser
transmission spectra under conditions where our interaction region optical
depth was typically less than 10^-3.
