K S Krishnan and the early experimental evidences for the Jahn-Teller Theorem

TL;DR

This paper highlights K S Krishnan's early experimental evidence supporting the Jahn-Teller theorem from the late 1930s, emphasizing its significance and overlooked contributions to molecular symmetry distortions.

Contribution

It uncovers and discusses Krishnan's 1939 work, which provided early experimental support for the Jahn-Teller theorem, previously largely unknown.

Findings

Krishnan identified experimental results supporting Jahn-Teller effects in 1939.

His work predated and aligned with modern experimental confirmations.

Krishnan's contributions are underrecognized in the history of Jahn-Teller research.

Abstract

Jahn-Teller theorem, proposed in 1937, predicts a distortional instability for a molecule that has symmetry based degenerate electronic states. In 1939 Krishnan emphasized the importance of this theorem for the arrangement of water molecules around the transition metal or rare earth ions in aqueous solutions and hydrated saltes, in a short and interesting paper published in Nature by pointing out atleast four existing experimental results in support of the theorem. This paper of Krishnan has remained essentially unknown to the practitioners of Jahn-Teller effect, eventhough it pointed to the best experimental results that were available, in the 30's and 40's, in support of Jahn-Teller theorem. Some of the modern day experiments are also in conformity with some specific suggestions of Krishnan.