def parse_SpinOrbit(upf_dict, root):
    """
    Spin orbit coupling.
    """
    if not upf_dict['header']['spin_orbit']:
        return
    proj_num = upf_dict['header']['number_of_proj']
    for i in range(proj_num):
        node = root.findall('./PP_SPIN_ORB/PP_RELBETA.%i' % (i + 1))[0]
        upf_dict['beta_projectors'][i]['angular_momentum'] = float(node.
            attrib['lll'])
        upf_dict['beta_projectors'][i]['total_angular_momentum'] = float(node
            .attrib['jjj'])
