Program dParFit16

dParFit16 is R.J. Le Roy's program for performing least-squares fits of a diatomic molecule spectroscopic data set consisting of any combination of microwave, infrared or electronic vibrational bands, fluorescence series, photo-association spectroscopy binding energies and/or input Bv values, involving one or more singlet electronic states and one or more isotopomers, to parameters defining the energy levels of each state. The levels for each electronic state may be described by one of:
  1. band constants Gv, Bv, Dv, ... etc. for each vibrational level of each isotopomer,
  2. generalized Dunham expansions,
  3. near-dissociation expansions (NDE), or
  4. mixed NDE/Dunham functions (MXS), or
  5. independent term values for each vibration-rotation level of each isotopomer.
and the effect of lambda doubling or doublet-sigma spin splitting is represented either by band-type constants for each vibrational level of each isotopomer, or by Dunham-type expansions in (v+1/2). Dunham, pure NDE or MXS fits automatically incorporate normal first-order semiclassical multi-isotopomer mass scaling, and allow for inclusion of atomic-mass-dependent Born-Oppenheimer and first-order JWKB breakdown corrections (collectively called BOB corrections) for each electronic state. A full description of the most recent version of this code has been published online in J. Quant. Spectrosc. Radiat. Transfer 186, 197 (2016), which is available at, while the corresponding source code and detailed Program Manual are available as Supplementary "Application" files at that www link. All future citations regarding use of this code should refer to this Journal Article.

If you wish to be Registered with the author as a user of this code, eligible to be sent any future bug fixes or updates, please fill in the following form Register dParFit-16 Registration. Note that the only non-cosmetic change from the most recent previous versions of this code are that the new version uses the 2010 values of ħ, and its atomic masses subroutine incorporates the 2012 version of the atomic mass table.
As ever, I would be pleased to receive information regarding apparent or real malfunctions of this code or weakness in the documentation, please contact the author by e-mail: 'leroy AT'

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