Maps of Nonadiabatic Coupling in Triatomic Hydrogen

We show in an experiment that dissociation of state-selected neutral $\mathrm{H}_3{}^{*}$ molecules into three ground-state hydrogen atoms reveals highly structured maps of correlation in the motion of the three atoms. These maps provide a direct view of the internal molecular couplings which initiate dissociation.

Figure 1

Cut of potential energy surfaces of ${\mathrm{H}}_3$ along the symmetric stretch coordinate (${\mathrm{D}}_{3h}$ geometry). Bound state wave functions of the $3s{A}_1^{\prime }$ state are shown together with three continuum functions of total energy $W$.

Figure 2

Final state momentum correlation measured in three-body decay of the $3s{A}_1^{\prime }$, $3d{E}^{\prime \prime }$, and $3p{E}^{\prime }$ electronic states of ${\mathrm{H}}_3$ (left) and ${\mathrm{D}}_3$ (right).

Figure 3

Final state momentum correlation measured in three-body decay of the $3s{A}_1^{\prime }$ and $3d{E}^{\prime \prime }$ electronic states of ${\mathrm{H}}_3$ for different degrees of vibrational excitation $\{{\nu }_1,{\nu }_2\}$.

Figure 4

Characteristic momentum vector orientations for specific points in the Dalitz plot. Note that in the Dalitz coordinates (4) all events are restricted by energy and momentum conservation to an area within a circle of radius $1/3$. For a homonuclear molecule a sixfold degeneracy appears. The three areas marked by circles at the azimuthal angles $0^{°}$, $120°$, and $240°$ correspond to dissociation into $\mathrm{H}+{\mathrm{H}}_2$. The circles at $60°$, $180°$, and $300°$ mark where one hydrogen atom remains at rest in the center-of-mass frame.

Figure 5

Predictions of Eq. (8) for the vibrational ground state $\{0,0\}$ and for the symmetric stretch excited state $\{1,0\}$ for ${\mathrm{H}}_3$ and ${\mathrm{D}}_3$ at $W=3.10\mathrm{e}\mathrm{V}$.