private void thermallyExciteAtoms() {
		if (thermalExcitor == null)
			thermalExcitor = new ThermalExcitor(this);
		double rxi, ryi, rxij, ryij, rijsq, sig;
		for (int i = 0; i < numberOfAtoms - 1; i++) {
			rxi = atom[i].rx;
			ryi = atom[i].ry;
			for (int j = i + 1; j < numberOfAtoms; j++) {
				if (atom[i].isExcitable() || atom[j].isExcitable()) {
					rxij = rxi - atom[j].rx;
					ryij = ryi - atom[j].ry;
					rijsq = rxij * rxij + ryij * ryij;
					sig = 0.5 * (atom[i].sigma + atom[j].sigma);
					sig *= sig;
					if (rijsq < sig) {
						thermalExcitor.excite(atom[i], atom[j]);
					}
				}
			}
		}
	}