  Calculating dipole moments with high-order basis sets is generally only
possible for the light molecules, such as water. A simple, yet highly effective
strategy of obtaining high-order dipoles with small, computationally less
expensive basis sets is described. Using the finite field method for computing
dipoles, energies calculated with small basis sets can be extrapolated to
produce dipoles that are comparable to those obtained in high order
calculations. The method reduces computational resources by approximately 50%
(allowing the calculation of reliable dipole moments for larger molecules) and
simultaneously improves the agreement with experimentally measured infrared
transition intensities. For atmospherically important molecules which are
typically too large to consider the use of large basis sets, this procedure
will provide the necessary means of improving calculated spectral intensities
by several percent.
