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Colin Western (
School of Chemistry, University of Bristol, UK

See Getting Started for pointers to key pages in the documentation.

3 Dec 2018: Paper describing updated automatic fitting and Nearest Lines Plots available on-line: “Automatic and semi-automatic assignment and fitting of spectra with PGOPHER”, Colin M Western and Brant E Billinghurst, Physical Chemistry Chemical Physics, 2019, doi:10.1039/c8cp06493h; the accepted manuscript is available here.

Version 10.1.180 (30 Nov 2018): Formal release of version 10.1. This includes a significant update to the automatic fitting, particularly the addition of Nearest Lines Plots; see Automatic fitting of the nu5 band of cis 1,2-Dichloroethene, Automatic fitting of an N2O IR spectrum and Automatic fitting of an N2O IR spectrum with additional diagnostic tools for detailed instructions. For a more formal description see 3 Dec 2018 entry above. A variety of other improvements have been made, including improvements in line intensity fitting and better handling of larger problems. See the release notes for a more detailed list of changes and bugs fixed. Upgrading is recommended for all users to make use of speed ups and bug fixes; the user interface has not changed significantly, apart from some changes to the automatic fitting process, and the .pgo files from older versions will work in the new version except for unusual cases, which will generate a message on loading.

4 Apr 2017: Paper describing Automatic Fitting as implemented in version 10.0 now available on line: "Automatic Assignment and Fitting of Spectra with PGOPHER". C. M. Western and B. E. Billinghurst, Physical Chemistry Chemical Physics, 2017, doi:10.1039/c7cp00266a. The accepted manuscript is also available.

Version 10.0.505 (14 Feb 2017): Formal release of version 10. The major new feature is Automatic Fitting as described in "Automatic assignment and fitting of spectra with PGOPHER", but there are many other improvements and fixes, including faster handling of large problems and faster importing of large files with spectra. See the release notes for a more detailed list of changes. 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.

3 Nov 2016: Final version of the paper giving a formal description of the program works now available on line: "PGOPHER, A Program for Simulating Rotational, Vibrational and Electronic Spectra", C. M. Western, Journal of Quantitative Spectroscopy and Radiative Transfer, 186 221-242 (2016) doi:10.1016/j.jqsrt.2016.04.010. The accepted manuscript is also available.

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 (11 June 2015): A 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.

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.

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:
See the release notes for a detailed list of changes, including notes on upgrading from previous versions.

Version 7.1 (13 September 2010):
Bug fix release - In the vibrational only mode, linear molecule Franck-Condon factor calculations for states with non zero vibronic angular momentum had incorrect intensities, as the degeneracies were not properly accounted for. A few other minor issues have also been fixed.

Version 7.0 (15 June 2010): Apart from many minor improvements and bug fixes, several features have been added at the request of users:
Version (6.0):


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 a supporting web site at Bristol (, for Microsoft Windows, Apple Mac and Linux, with a beta version available for the . The data files are the same, regardless of the platform. The program is released as open source, and can be compiled with open source tools.

Graphical User Interface Features

Calculation Features

Supported Platforms

System Requirements

Most calculations will run on any  machine; larger calculations involving multiple states can benefit from more memory or processors. Some features, particularly Interactive fits, are much easier with a two or three button mouse rather than a trackpad or touch screen.