When a photon is incident on a 1 + 1 dimensional system described by the Sine–Gordon theory, transitions can occur from the ground state to soliton–antisoliton bound states called breather modes. We derive the lowest order Wentzel–Kramers–Brillouin (WKB) wave funetionals for these states and use them to estimate the transition rates. The transition to the lowest energy breather mode always dominates. The transition rates to the higher energy modes are suppressed by at least 10−2. A Monte Carlo simulation of the theory confirms this suppression. This effect is thus too small to account for the conductivity observed in the quasi-one-dimensional organic conductor tetrathiafulvene-tetraeyanoquinodimethane TTF-TCNQ.