Emilio Segrè Visual Archives

More than 30,000 photos of scientists and their work

Attention ESVA patrons:

The Emilio Segrè Visual Archives’ site is moving soon and adopting an open access approach to digital image sharing. Once we have transitioned to the new site in 2021, we will no longer charge for our high-resolution digital images or usage fees (note that we do not hold copyright to all the images in our collections and you will still need to obtain permission for those which we do not own).

If you are working on a long-term project, we advise you to wait until the migration is complete so that you may obtain our copies for free. If you cannot wait, email us at nbl [at] aip.org and we will do what we can to assist you. We will not be offering refunds for past purchases.

For more information, please visit our FAQ page on the Ex Libris Universum blog. 

Dempster Arthur F1

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Dempster Arthur F1

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We charge a usage fee per photo if the photo is published, reproduced in a product or publicly exhibited. This is not a license in the legal sense. As a non-profit institution, we do not make any money providing these photographs. It is only by assessing usage fees that we are able to cover the cost of providing publication quality copies of our photos, preserving the photograph collection according to archival standards, and providing access to the collection by maintaining an online image database. The copyright holder may charge a fee in addition to our service fee.

Images are for use in educational projects only and must be used in a respectful manner.

Image title: 
Dempster with equipment
Credit line: 
University of Chicago Dept. of Public Relations, AIP Emilio Segrè Visual Archives

Original caption: "Arthur J. Dempster, discoverer of uranium 235 and professor of physics at the University of Chicago, was a specialist in the nucleus of the atom. He perfected a weighing method by means of which he has discovered atoms of differing weight (isotopes) in elements previously believed to have uniform atomic weights. The precise weight of the isotopes is the basis for calculating the energy set free in nuclear reactions. Prof. Dempster also achieved a reputation as the principal American authority on positive rays."

Original format: 
1 photographic print (black and white; 8 x 9.5 inches)
Dempster, Arthur Jeffrey