On multipole interaction methods in exciton theory

摘要: Three features of the multipole method treating excited state molecular interactions in crystals are examined. The first is error caused by as those point multipoles even for nearest neighbour molecules with some overlapping electron clouds. second question convergence series, and conditions under which terms higher than dipole-dipole must be included. third influence coupling static moments one molecule transition between different states another. It concluded from a discussion principles, supported calculations examples, that `conventional' methods using only adequate when (i) transitions at least moderately intense (ii) dipole lattice sums not made very small special orientation. When these satisfied quadrupole octupole Their effects on factor-group splittings may many times greater term; intensity where changes occur order, approximation remains more acceptable but not, general, negligible.