BitSet getAtomBitSet(String atomExpression) {
		selectionModeAtoms = true;
		Eval e = new Eval(viewer);
		BitSet bs = new BitSet();
		try {
			bs = e.getAtomBitSet(atomExpression);
		}
		catch (Exception ex) {
			Logger.error("SelectionManager.getAtomBitSet " + atomExpression);
			Logger.error("" + ex);
			return bs;
		}
		return bs;
	}