Knowledge Bank

The predicted intensity of a new absorption feature in the spectrum of solid $o-D2$ corresponding to three molecules making simultaneous rotational transitions from $J=0$ to $J=2$ is calculated. This transition should occur near $555cm-1$, and arises primarily through the mixing of rotational levels by the quadrupole-quadrupole interaction. Although the calculated intensity is small (less than 1% of that of the weak $Wo(o)$ transition), it nevertheless may be observable. Such an observation would be of interest, because by comparing the experimental intensity with that predicted on the basis of mixing of levels, one can set an upper limit to the contribution to such a feature from non-additive (three-body) dipoles.