Linking Ultracold Polar Molecules

We predict that pairs of polar molecules can be weakly bound together in an ultracold environment, provided that a dc electric field is present. The field that links the molecules together also strongly influences the basic properties of the resulting dimer, such as its binding energy and predissociation lifetime. Because of their long-range character, these dimers will be useful in disentangling cold collision dynamics of polar molecules. As an example, we estimate the microwave photoassociation yield for OH-OH cold collisions.

Figure 1

(a) Adiabatic potential energy curves for the six-channel model of $[\mathrm{O}\mathrm{H}{]}_2^{*}$, as described in the text. Avoided crossings in these curves create the potential well labeled $V_b$, which holds bound states of the dimer. (b) shows the electric-dipole coupling matrix element between $V_b$ and the ground state $V_0$.

Figure 2

Binding energies of bound states in the potential $V_b$ versus electric field. Solid lines: Close-coupling results. Dashed lines: Single-channel adiabatic approximation. Error bars: Approximate predissociation widths, as computed from the eigenphase sums in the close-coupling calculations.