  We characterize the low temperature phase of a simple model for RNA secondary
structures by determining the typical energy scale E(l) of excitations
involving l bases. At zero temperature, we find a scaling law E(l) \sim
l^\theta with \theta \approx 0.23, and this same scaling holds at low enough
temperatures. Above a critical temperature, there is a different phase
characterized by a relatively flat free energy landscape resembling that of a
homopolymer with a scaling exponent \theta=1. These results strengthen the
evidence in favour of the existence of a glass phase at low temperatures.
