NIST Atomic Spectra Log-Cosine Spectral Scan

This repository contains a reproducible log-cosine spectral-density scan over public NIST Atomic Spectra Database line lists for transition metals (Fe, Ni, Co, Cr, Mn, Ti). The primary result is a stable Fe II log-cosine spectral-density mode in logarithmic wavenumber coordinates.

This project uses public CSV exports from the NIST Atomic Spectra Database. It is not "NIST certified", endorsed, or validated by NIST. NIST is the data provider only.

What the scanner does

For each line list (e.g. data/Fe_lines.csv) the scanner reads wavenumber wn(cm-1) (handling NIST/Excel-style cells such as ="49998.80"), optionally filters by ionization stage sp_num, converts to the logarithmic coordinate

ell = ln(wavenumber_cm^-1)

bins line counts on ell, and fits a one-mode Poisson log-linear model:

log mu(ell; k, a, b, c) = log mu0(ell) + c + a cos(k ell) + b sin(k ell)

against a Gaussian-smoothed baseline mu0. The scan statistic is the deviance improvement

DeltaChi^2_star = max_k ( D[y || mu0] - D[y || mu(k)] )

over a k grid. The active-domain winding is

n = k * Delta_ell / (2 pi)

where Delta_ell = ell_max - ell_min. The null is a parametric Poisson bootstrap from mu0, scanned with the same k grid; the empirical p-value is

p_hat = (1 + tail_count_ge) / (1 + null_n)

Primary result (Fe II, ion = 2, n_unique_lines = 9447)

Bins	k_best	n_obs	DeltaD	null (tail/N)	p_hat
120	31.3265306122449	10.717134	355.7443	0 / 5000	1/5001 ≈ 0.00019996
160	31.3265306122449	10.739649	315.7277	0 / 5000	1/5001 ≈ 0.00019996
200	31.3265306122449	10.753158	259.1788	0 / 5000	1/5001 ≈ 0.00019996

The headline observation is bin-stability of k_best = 31.3265306122449 across 120 / 160 / 200 histogram bins, with n_obs stable near 10.7 and zero null exceedances at 5000 nulls per bin setting. The PASS/FAIL gate encoded in scripts/make_verdict.py enforces this.

Repository layout

README.md
RESULTS.md
requirements.txt
data/
  Fe_lines.csv  Ni_lines.csv  Co_lines.csv
  Cr_lines.csv  Mn_lines.csv  Ti_lines.csv
scripts/
  nist_wct_log_spectral_scan_FIXED.py    # canonical CPU scanner
  nist_wct_log_spectral_scan.py          # legacy one-shot Fe splitter
  nist_wct_log_spectral_scan_CUPY.py     # optional GPU mirror (CuPy)
  nist_batch_run_neighbors.py            # neighbor-ion batch runner
  run_feii_bin_stability.py              # Fe II 120/160/200 ladder + master CSV
  make_verdict.py                        # PASS/FAIL from master CSV
outputs/
  fe_ion2_120/  fe_ion2_160/  fe_ion2_200/   # canonical Fe II runs
  batch_neighbors/                            # canonical neighbor batch (written on demand)
tables/
  nist_master_results.csv
  nist_verdict.csv
tests/
  test_nist_scanner.py

CPU canonical script vs optional CuPy script

• scripts/nist_wct_log_spectral_scan_FIXED.py is the canonical scanner. It is pure NumPy/SciPy and produces the values in the table above. The PASS/FAIL verdict is built off this script's output.
• scripts/nist_wct_log_spectral_scan_CUPY.py is an optional GPU mirror using CuPy. It is faster for large null_n but is not required for reproduction. If CuPy is not installed, ignore this script.

Commands

Quick single-bin run (Fe II, bins=160, 500-null preview):

python scripts/nist_wct_log_spectral_scan_FIXED.py \
    --csv data/Fe_lines.csv --ion 2 --bins 160 \
    --null-n 500 --min-lines 100 \
    --out-dir outputs/fe_ion2_160

Bin-stability ladder (quick, 500 nulls per bin):

python scripts/run_feii_bin_stability.py --null-n 500

Full run (5000 nulls per bin) plus verdict:

python scripts/run_feii_bin_stability.py --null-n 5000
python scripts/make_verdict.py

Tests:

pytest -q

Neighbor batch (Ni / Co / Cr / Mn / Ti, ion=2) — exploratory:

python scripts/nist_batch_run_neighbors.py --preview-null 500 --no-promote

Canonical vs legacy outputs

• The canonical Fe II outputs live in outputs/fe_ion2_{120,160,200}/. Only these (or whatever rows are listed in tables/nist_master_results.csv) feed the PASS/FAIL verdict.
• Older / exploratory runs at the repo root (for example outputs_fe_ion2_120_cupy_full/, outputs_ni_ion2_160_preview/, outputs_nist_wct/, etc.) are preserved as provenance. They are legacy, non-canonical, and are intentionally not used by the verdict unless they are explicitly referenced in tables/nist_master_results.csv. Do not delete them.

Limitations

• This is a line-density scan, not a flux-spectrum scan.
• The data are public NIST Atomic Spectra Database CSV exports; line completeness varies by species and is not uniform across ell.
• The null is a parametric Poisson bootstrap from a Gaussian-smoothed baseline. Baseline-sigma sensitivity is documented and should be audited for any extension beyond Fe II.
• This repository makes no claim of NIST endorsement, certification, or validation.