While on leave at Princeton University, he found a fruitful collaboration with Sam Treiman and H. W. Wyld on weak interactions, particularly the various observable decay correlations in allowed nuclear beta decay involving the electron's momentum, its spin, the neutrino's momentum, and the nuclear spin that provide information about parity conservation or non-conservation and time reversal conservation or not. He also published an early paper on the theoretical foundation for the then recently discovered muon-catalyzed fusion of hydrogen isotopes.