Paper 2.12: N. Bloembergen, W.K. Bums and C.L. Tang, “Symmetry of nonlinear optical susceptibilities in absorbing media and conservation of angular momentum,” International Journal for Quantum Chemistry 5, 555–562, 1971.

I received an invitation to participate in an international school of quantum chemistry held on Sanibel Island Florida in the winter of 1970–71. The director of the school, Dr. Per-Olov Lowdin, wanted to honor John C. Slater and John H. Van Vleck in the program. This paper is dedicated to the latter, a long-time mentor and colleague, from whom I learned much about magnetism and angular momentum. Van, who often called me “fellow Dutchman”, had a soft spot for the Netherlands in general and Dutch physics in particular. He was proud of his Dutch ancestry, which he could trace to some immigrants on the “Half Moon”, the second ship to sail up the Hudson River in the first decade of the seventeenth century.

The extension of the symmetry considerations for harmonic generation by circularly polarized light to the imaginary part of the nonlinear susceptibilities appeared to be an appropriate subject for my lecture at the above-mentioned school. Professor C.L. Tang from Cornell University spent a sabbatical leave at Harvard at that time. My graduate student Bill Burns was also a co-author of paper 2.8.