About NN-OnLine

Last updated 13 Aprli 2026

1. Who, what, where, when, why

In 1993 the Nijmegen Group published its nucleon-nucleon partial-wave analysis (PWA93) which then became the de facto standard, and still is. Based on these results several high-precision NN potentials were constructed. With envy we looked at the telnet-based SAID facility of Richard Arndt at Virginia Tech where everyone from the whole world could dial in and get access to their results. We wanted something similar. And went for the then emerging World-Wide Web technology. In the summer of 1994 we made our first website. NN-OnLine was born. In the course of time slowly building up to what it is now. Initially (and still) focussed on the nucleon-nucleon interaction, hence the name NN-OnLine, but trying to include more of everything the Nijmegen Group has been working on. With the retirement of Johan de Swart in 1996 the Nijmegen Group formally ceased to exist, but its remnants are still active.

2. Technical details

Our first webserver was a HP 9000 735/99 workstation ('photon'), the then fastest workstation on the market, with a 100 MHz CPU and 32 MB of memory, running HP-UX. Stored in a cupboard at the department. Around 2000 replaced by a HP C360 workstation, cheaply bought off eBay. When the whole faculty moved to a new building we got ourselves a dedicated Linux server. Since 2015 we use a shared Linux server of the Faculty of Natural Sciences. All the time using Apache as webserver software. The site uses some PHP to tie everything together. But the most important programs are written in fortran and a little c. External sources used are the DISLIN library (for 3d plots) and drawp3d (for 3d VRML visualizations).

3. Conditions of use

NN-OnLine is the product of scientific activity, please treat it as such. If NN-OnLine turns out to be a useful resource for you, please cite the proper reference to the publication of the used potential, PWA, or experimental data. And a reference to NN-OnLine by at least mentioning the URL https://nn-online.org would be greatly appreciated.

4. You can contribute to NN-OnLine

By letting us know if NN-OnLine was useful for you; if you have complaints, or suggestions to improve NN-OnLine. If you find any errors, or have additional or new information that would make NN-OnLine more useful, please let us know.

5. Contact: Questions, comments, .....

Your feedback is greatly appreciated. Also if you have any questions on using NN-OnLine, feel free to ask. Contact us at info@nn-online.org.

6. Disclaimer

Although we do our best to make the programs and all other information free of errors and bugs we cannot guarantee that all information is correct. If you obtain erroneous or questionable results from NN-OnLine please contact us and we will have a look at it.

7. Acknowledgements

	Everyone who ever was part of the Nijmegen Group.
	The Department of Experimental High Energy Physics of the Radboud University Nijmegen for mental and material support the initial years.
	The Department of Computers and Communication of the Natural Science faculties of the Radboud University Nijmegen for occasional hardware donations, backup services, and currently hosting NN-OnLine.
	This work was part of the research program of the former "Stichting voor Fundamenteel Onderzoek der Materie" (FOM) which was financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) (1994-1995).
	Facilities provided by the Australian Research Council and the Flinders University of South Australia helped to keep the site up to date (1996-1997).
	Facilities provided by the University Medical Center Utrecht helped to keep the site up to date (2005-2007).
	Facilities provided by the Erasmus University Medical Center, Rotterdam helped to keep the site up to date (2008 -).

And of course all users who made invaluable suggestions and reported bugs and other inconsistencies.