A simple theory is developed which predicts impact sensitivities in crystalline explosives from vibrational spectra measured at room temperature. The theory uses Raman spectra of energetic materials to construct vibrational energy level diagrams, which are then used as input for a model designed to calculate the rate of energy transfer from phonon and near-phonon vibrational energy levels to higher energy vibrational levels. Energy transfer rates are determined using Fermi's Golden Rule and results from simple theories of near-resonant energy transfer. The application of the theory and model, using Raman spectra of seven different neat explosive samples, gives results in good agreement with results of drop weight impact tests.