The electric dipole polarizability has been determined in a unique way
. Binary complexes of argon with transition metal cations have been st
udied by optical spectroscopy. The vibrational structure of electronic
transitions near the dissociation limit of the upper state quantifies
the forces between the atoms. The polarizability of argon is determin
ed from the charge-induced-dipole force in four different molecular io
ns as 1.49 +/- 0.10 Angstrom(3). This is lower than the accepted value
by 9%. This discrepancy may imply that the multipole expansion of the
charge distortion does not have linearly independent coefficients in
the field of an ion at close range. Induced higher-order moments appea
r to reduce the effective dipole polarizability.