Isotope shift / field shift module: calculate 1st- and 2nd-order (QFS) field shift constants using MBPT - Githubissues

benroberts999 / ampsci

A c++ program for high-precision atomic structure calculations of one and two valence systems. Uses Hartree-Fock + correlation potential method. Can calculate ionisation cross sections with large of energy/momentum transfer.

https://ampsci.dev

MIT License

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Isotope shift / field shift module: calculate 1st- and 2nd-order (QFS) field shift constants using MBPT #45

Closed zacharysh closed 1 month ago

zacharysh commented 2 months ago

Replaces Module::fieldshift, Module::fieldShift2 (see, e.g., cda5c0b, 748e981) and DiracOperator::F_fs operator (e.g., 2f5f4ca).

Calculates 1st- and 2nd-order change in energy dE, along with corresponding changes d<r^2>, d<r^4> due to change in nuclear charge radius.

Physics:

First-order: use linear regression to fit parameters: dE^(1) ~ F d<r^2> + G^4 d<r^4>.
Second-order: dE^(2) ~ G^2 [d<r^2>]^2 correction is approx. constant and calculated at runtime. Uses GSL for mean/sd.

Please let me know if there are any concerns or suggested changes.