 On Willis ' advice , Rabi traveled to Leeds for the 97th annual meeting of the British Association for the Advancement of Science , where he heard Werner Heisenberg present a paper on quantum mechanics . Afterwards , Rabi moved to Copenhagen , where he volunteered to work for Niels Bohr . Bohr was on vacation , but Rabi went straight to work on calculating the magnetic susceptibility of molecular hydrogen . After Bohr returned in October , he arranged for Rabi and Yoshio Nishina to continue their work with Wolfgang Pauli at the University of Hamburg . 
