Fix incorrect units for BSE-calculated spectra

[ndaelman-hu]

Summary

Both Exciting and OCEAN parsers were incorrectly setting intensities_units = 'F/m' for BSE-calculated absorption spectra. These parsers actually calculate the macroscopic dielectric function ε(ω), which is dimensionless.

Background

The confusion arose from conflating two different quantities:

• Dielectric function/constant (dimensionless) - what BSE calculates
• Absolute permittivity (F/m units) - different quantity

Changes

Exciting parser (electronicparsers/exciting/parser.py:2333)

sec_spectra.intensities = data[2]  # Imaginary part of dielectric function  
sec_spectra.intensities_units = 'dimensionless'

OCEAN parser (electronicparsers/ocean/parser.py:239)

sec_spectra.intensities = data_spct[:, 2]  # BSE absorption/emission spectra (dielectric function)
sec_spectra.intensities_units = 'dimensionless'

Testing

• All Exciting parser tests pass (8 passed, 1 skipped)
• All OCEAN parser tests pass (1 passed)

References

• Fixes Exciting parser sets incorrect units for dielectric function imaginary part #334
• Related schema discussion: Define proper units handling for dimensionless spectra quantities nomad-schema-plugin-run#24
• OCEAN documentation confirms dielectric function is dimensionless: PMC9844114

[ndaelman-hu]

Breaking Change Warning

Changing `intensities_units` from `'F/m'` to `'dimensionless'` will affect all existing Exciting and OCEAN archives. This drops backwards read compatibility.

Recommendation: This change should be applied when we do a full reprocessing of Exciting and OCEAN archives to ensure consistency across the database. @ladinesa @JFRudzinski

[coveralls]

Coverage Report for CI Build 26090687936

Coverage increased (+0.04%) to 92.881%

Details

• Coverage increased (+0.04%) from the base build.
• Patch coverage: 4 uncovered changes across 2 files (0 of 4 lines covered, 0.0%).
• 36 coverage regressions across 2 files.

Uncovered Changes

File	Changed	Covered	%
electronicparsers/exciting/parser.py	2	0	0.0%
electronicparsers/ocean/parser.py	2	0	0.0%

Coverage Regressions

36 previously-covered lines in 2 files lost coverage.

File	Lines Losing Coverage	Coverage
electronicparsers/exciting/parser.py	23	71.0%
electronicparsers/exciting/metainfo/exciting.py	13	90.74%

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Coverage Stats

Relevant Lines:	38908
Covered Lines:	36138
Line Coverage:	92.88%
Coverage Strength:	0.93 hits per line

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💛 - Coveralls