Kai Siegbahn, co-winner of the Nobel Prize in Physics 1981, born on July 20, 1918, died of heart failure on July 20, 2007, after visiting his summer home in Angelholm, in southern Sweden.

Kai Siegbahn

There is a good brief account of the the contribution of "ESCA" - Siegbahn's own name for the spectroscopy he pioneered - as an "extremely useful analytical tool" in "The Times" of August 9th, and another (with slightly different emphasis) in the "New York Times" of August 7th.

Although I never managed to visit him in his laboratory, I did have the privilege of lunching with him in Glazebrook Hall (NPL's canteen) during the 1983 ESCA Users' Group meeting at NPL Teddington, and a more pleasant, open, and unassuming person one could hardly imagine, full of interest in the commercial state of the technique he had launched and in science in general.

When I wrote to him some years later asking for a photograph (the one alongside - there's a larger version available here, in a new window) to include in a wall-chart history of XPS we were producing, he quickly provided it and also a very pleasing (and unprompted) appreciation of our efforts in the letter reproduced below.