VALD3 line lists include lines that are forbidden by quantum mechanical selection rules or lines that involve two-electron excitation (the so-called "autoionizing" lines). Such transitions are marked by a letter that follows the [[VALD3_accuracy|Accuracy field]] in the Long Format output. The table below explains the meaning of the letters:

||Field content||  Transition type         ||
||  blank      ||  Allowed transition      ||
||    A        ||  Autoionizing transition ||
||    B        ||  Forbidden: Electric quadrupole transition (E2)||
||    C        ||  Forbidden: Magnetic dipole transition (M1)    ||
||    D        ||  Forbidden: Magnetic quadrupole transition (M2)||
||    E        ||  Forbidden: Electric octupole transition (E3)  ||
||    F        ||  Forbidden: Magnetic octupole transition (M3)  ||