def info_atomic_shell():
    """
    Return a dict to describe the information of atomic shell.
    The key is a string of the shell's name, the value is a 2-elments tuple,
    the first value is the orbital angular moment number and
    the second value is the dimension of the Hilbert space.

    Returns
    -------
    info: dict
        The dict describing info of atomic shell.
    """
    info = {'s': (0, 2), 'p': (1, 6), 'p12': (1, 2), 'p32': (1, 4), 't2g':
        (2, 6), 'd': (2, 10), 'd32': (2, 4), 'd52': (2, 6), 'f': (3, 14),
        'f52': (3, 6), 'f72': (3, 8)}
    return info
