Every partial's delta_phi was solved from its OWN frame's lattice - by the predictor,
and again by SmoothGeometry. Per-frame geometry is re-refined against that frame's spots
alone, so what is left of its jitter entered each frame of an event independently and the
frames of one rocking event stopped sitting exactly one oscillation apart on the curve.
Their partialities then no longer tile it, and because a broad rocking curve spans more
frames, the error grows as 1/zeta - which is how it has been showing up: a zeta-graded
systematic that nothing in the integrator could reach.
For the frames of one event the geometry is exact. Each frame has already turned one
oscillation further, so delta_phi is linear in frame number with slope minus the
increment; the sign is checked against the data rather than derived, the measured mean
frame-to-frame slope being -0.19996 deg/frame at an increment of 0.20000. Fit the one
free number, the offset, over the event and lay its partials back on that line. The rms
departure removed is 0.25 deg - larger than the oscillation itself, because a small
orientation wobble is amplified by 1/zeta. The raw-hkl runs the merge already builds give
the grouping, so this costs one pass over the partials and no extra sort.
Full 38-crystal rotation battery against the same binary without it, on unchanged data
(observations +0.20%, unique reflections +0.03%, so none of this is selection):
R_meas_lo better 22 / worse 5, summed -41.0 pp; excess against XDS -46.9 -> -87.9
R_meas better 22 / worse 5, summed -24.7
CC1/2 better 17 / worse 2, summed +36.8
ISa better 15 / worse 22, summed +6.87; shortfall against XDS 28.1 -> 21.2
space groups unchanged at 35/38
The low-resolution R_meas gains land on the crystals that have carried this gap: 19.3 ->
10.8, 20.7 -> 13.8 (now past XDS), 25.6 -> 19.7, 17.5 -> 12.4 per cent. Exactly one
crystal shows any change in the two-pass branch fingerprint, so unlike most changes on
this path the result is not confounded by that bistability.
ISa falls on more crystals than it rises, and that is the estimator becoming honest
rather than the data getting worse: every crystal whose ISa dropped materially was
over-optimistic against its own R_meas_lo and moved toward consistency, and the median
ratio of reported ISa to the value its own R_meas_lo implies goes 1.09 -> 1.01, against
1.19 for XDS. The one real loss is a crystal going 1.11 -> 0.95 on that ratio.
High-shell CC1/2 is worse on 22 crystals, by about 1.2 points each. It is the one metric
that dissents, and it is also the one that has failed as an arbiter repeatedly on this
data, while overall CC1/2, R_meas, R_meas_lo and reflection count all improve on an
unchanged number of observations.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
b40abe31cf
