  The electromagnetic excitation of the two-phonon isovector giant dipole
resonance in relativistic projectiles incident on heavy targets can be proceed
via several intermediate $1^-$ one-phonon giant resonance states. In two step
electric dipole transitions the population of $0^+$, $1^+$, and $2^+ $
two-phonon states are possible. We calculate the amplitude distribution of
$1^-$ excitations with an RPA formalism, and use it to calculate the
electromagnetic excitation of two-phonon states in second order perturbation
theory and coupled-channels. We show that a conspiracy between angular momentum
coupling and the strength of the electromagnetic fields suppresses
contributions of $1^+$ states to the total cross sections.
