GEF 2013/2.2

This version has been updated several times due to new developments and improvements of the model, partly suggested by the users. We apologize for any incovenience. We wanted to make the modifications quickly available, but we also did not want to create a large number of releases. The version will probably be frozen soon. Please report problems to [schmidt-erzhausen (at)] and let us know your suggestions! Further development of the code relies strongly on the feedback from the users.

General description of fission observables. Released September 18, 2013, updated December 6, 2013.
(Even odd effect in fission-fragment neutron-number distribution revised.
 Mass distribution at high excitation energies revised.
 October 3, 2013: Angular momentum added as input parameter.
 October 12, 2013: Calculation of prompt-neutron emission improved, some model parameters modified.
 October 17, 2013: Problem causing incomplete output of covariance matrices solved. Physics not changed.
 October 30, 2013: Output of pre-fission neutron and proton emission extended in tables and list-mode.
 November 8, 2013: Modifed prompt-neutron emission due to shape fluctuations with energy dependence of shell effects.
 November 8, 2013: List-mode output of energies and directions of post-scission neutrons.
 November 10, 2013: Fission-gamma competition refined.
 November 18 and 19, 2013: New global parameter set. Multi-chance fission modified.
 November 20, 2013: Numerical instability corrected without change of the physics of the model.
 November 29, 2013: Calculation of multi-chance fission corrected and modified.
 December 4, 2013: Spurious even-odd effect in fission probabilites due to even-odd effect in theoretical shell correction removed.)


Stand-alone version (Monte-Carlo method)

The stand-alone version of the GEF code is written in FreeBASIC (a). The FreeBASIC compiler produces binary code from the same source on Windows (b) and on Linux. The executable uses the C library.  For  the Windows version, a GUI is provided, written in JustBasic (c). The Windows version runs also on Linux with Wine (d).

Quick start on Windows:

Quick start on Linux:

Sample output plot:

Mass distribution calculated with GEF

Calculated prompt-neutron spectra:

Prompt-neutron spectra for 235U(nth,f) and 252Cf(sf)

Windows version


Input mask of the graphical user interface:

GUI for the GEF code

Linux version


For Windows and Linux

Complete package


Readme file (Technical information, list of relevant publications)
EFNUDAT report (First comprehensive documentation)
Report JEFDOC 1423 (Updated documentation)

Source (for Windows and Linux)

Source files


Input files for extended input options
Distribution of entrance energies (example)
List of input parameters (example)
See Readme file for more detailed information.
Data tables in XML format (example)
List-mode file (example)
Raw data for the multi-variant distribution of fission-fragment yields from calculations with perturbed parameters (example)
See Reame file for more detailed information.

You may consider using the Windows version of GEF on Linux with Wine in order to profit from the more comfortable input handling offered by the graphical user interface. This option may also solve problems of missing libraries under Linux.

Subroutine (Folding method)

The subroutine aims for being used in combination with other nuclear-reaction codes. For a given fissioning nucleus with excitation energy E* and angular momentum I it calculates a number of fission observables with the GEF model.

Complete package


Technical description of the subroutine

FreeBASIC version


FORTRAN version


(a) FreeBASIC is a free compiler (
(b) Windows is either a registered trademark or a trademark of Microsoft Corporation in the United States and/or other countries.
(c) JustBasic is a free interpreter (
(d) Wine is a windows compatibility layer for Linux (