def interaction_strength(idx: int, mol_map: dict, acceptor_exp: float) -> float:
    """Calculate interaction strength for atom with index `idx`."""
    acceptor_strength = mol_map[idx]["sa"]
    num_lp = mol_map[idx]["num_lp"]
    if num_lp != 0:
        return acceptor_strength * (num_lp ** acceptor_exp)
    return 0.0