PGOPHER, a program for rotational, vibrational and electronic spectra

Laser Group homepage
Version 9.1.100 (8 Jan 2016): Formal release of version 9. In addition to the new features listed below, a comprehensive tutorial Walkthrough of Simulating and Fitting a Simple Spectrum has been added to the documentation, including an N2O sample spectrum to work with, and other new features include Custom Width Functions to provide a simple empirical way of specifying quantum number dependent line widths and intensities and a significant rework of the Transitions Window to allow selection by more quantum numbers and other options. See the release notes for a more detailed list. As ever, .pgo files from older versions will work without modification in the new version, except in a few unusual cases, which will give a warning message on loading. The ..pgo files remain essentially compatible with older versions, though expect warning messages if newer features are used

Version 9.0.101 (5 July 2015): Update of Mac version only, to avoid hard crash on some error messages. Mac users should update. Minor updates to documentation also.

Version 9.0.100 (17 June 2015): Draft release of version 9. New features include faster calculations for larger problems, Loomis-Wood plots, a wider selection of units for calculated quantities (for example Angstroms and  Oscillator Strength), a Vibrational Partition Function for calculating complete partition functions, a Check Derivatives command to assess the accuracy of numerical derivatives, other tools to assist in fitting and many other smaller improvements and bug fixes. See the release notes for a more detailed list. .pgo files from older versions will work without modification in the new version, except in a few unusual cases, which will give a warning message on loading. A permanent DOI will be made available for the new version shortly. Bug reports welcome to

26 Jan 2015: If simulating hyperfine structure on a molecule with equivalent nuclei, then the statistical weights are not calculated correctly if equivalent spin 0 nuclei are explicitly included in the calculation. This is fixed in version 8.0.308; for earlier versions simply delete any nucleus objects with spin zero. The documentation on how to handle equivalent nuclei when calculating hyperfine structure has also been clarified - see linear and asymmetric top documentation.

20 Nov 2014: Versions before 8.0.258 swapped the +l and -l labels in symmetric tops for levels of E2 and E5 vibronic symmetry (not rovibronic symmetry) as compared to the definition given by Hoy and Mills J. Molec Spectrosc. 46, 333 (1973). The calculated energy levels and intensities are not affected, just the labels of the states. This is fixed in the deveopment versions; note input files for fitting produced by or for older versions may require adjustment for degenerate vibronic states in the affected point groups (D4d and other groups with 5 fold or higher rotation axes).

23 July 2014: In addition to the website, PGOPHER can now be cited via a permanent digital object identifier, doi:10.5523/bris.huflggvpcuc1zvliqed497r2.

23 April 2014: Two bugs have been found concerning simulating Stark and Zeeman effect spectra. Spectra in the presence of external fields involving symmetric tops with degenerate vibronic states included spurious extra transitions, and the M dependence of the intensity of multiphoton transitions, or ordinary transitions with random polarisation, was calculated incorrectly. These have been fixed in development versions above 8.0.186.

Version 8.0.102 (11 December 2013): Minor update to fix crashes in energy level plots in the Mac version, and some issues with vibrational calculations. See the release notes for a more detailed list of problems fixed; there are no new features

Version 8.0 (2 December 2013): A significant new release of PGOPHER, with the major new feature being the addition of the calculations involved in a Force Field Analysis to PGOPHER. This allows vibrational frequencies and many other related quantities including Franck-Condon factors and centrifugal distortion distortion constants to be calculated from a force field expressed in terms of bond bending and stretching coordinates or symmetry coordinates. Fitting the force field to any reasonable combination of observations is also possible, and this has been set up so that scaling or otherwise adapting ab initio force fields is straightforward. Other significant new features include:
  • Custom population functions, allowing an essentially arbitrary function to be used as an alternative to the Boltzmann distribution.
  • Flexible use of HITRAN and ExoMol linelists.
  • Axis switching effects
  • Custom transition moment functions to allow for Herman-Wallis factors
  • Tweaks for Mac usage, including more (Mac) standard shortcut keys and dropping of files onto main window.
  • 64 bit version now part of the standard release, allowing larger calculations to be performed.
See the release notes for a detailed list of changes, including notes on upgrading from previous versions.


PGOPHER is a general purpose program for simulating and fitting rotational, vibrational and electronic spectra. It represents a distillation of several programs written and used over the past decade or so within the Bristol laser group and elsewhere, but is a re-write from scratch to produce a general purpose and flexible program. PGOPHER will handle linear molecules and symmetric and asymmetric tops, including effects due to unpaired electrons and nuclear spin, with a separate mode for vibrational structure. The program can handle many sorts of transitions, including Raman, multiphoton and forbidden transitions. It can simulate multiple species and states simultaneously, including special effects such as perturbations and state dependent predissociation. Fitting can be to line positions, intensities  or band contours.

PGOPHER is designed to be easy to use; it uses a standard graphical user interface and the program is currently in use for undergraduate practicals and workshops as well as research work. It has features to make comparison with, and fitting to, spectra from various sources easy. In addition to overlaying numerical spectra it is also possible to overlay pictures from pdf files and even plate spectra to assist in checking that published constants are being used correctly.

The program is freely downloadable from this web site for Microsoft Windows, Apple Mac and Linux. The program is released as open source, and can be compiled with open source tools. For support please contact

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