Speaker
Description
There are basically two ways to determine precision values for nuclear quadrupole moments (Q): Measurements for stable or reasonably long-lived (mostly ground) states by atomic and molecular spectroscopy and measurements for much shorter-lived excited states using nuclear condensed matter techniques like Moessbauer (MS) or perturbed angular distribution (PAD) (and correlation, PAC) spectroscopy. In all cases the direct experimental result is the product of the electric field gradient (efg) at the nuclear site with Q. The efg for atomic and simple molecular systems can now mostly be calculated by theory with good accuracy, while the present status of density functional calculations of solid-state systems used for short-lived excited states limits the accuracy to the 10 to 20% level.
In project IS640 we have overcome this problem by measuring isolated Cd and Hg molecules with PAC. Similar experiments for Pb are planned in IS708, and related ones for In in IS673. A short summary of the still missing relations between the results of Q for short-lived relative to long-lived states for critical elements will be presented.
