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Kai Siegbahn's early instrument used iron-free magnetic double focusing and a thin-window Geiger-Müller counter. His later instrument, compatible with ultra-high vacuum, used a spherical electrostatic electron energy analyzer and monochromatic aluminum X-rays. Argon mixed with methane supplied simultaneous $2p$ reference lines.^[ref]

Two sulfur lines in sodium thiosulfate distinguished chemical environments within one compound. A separate gold comparison showed a fingerprint obscuring substrate lines.^[ref]

For an unknown sample, first document its preparation and transfer, then compare survey and detailed scans under reproducible illumination, contact and acquisition conditions. Repeat a region to test change during exposure. If a cleaning treatment is used, compare before and after rather than assuming that cleaning preserves the original chemical bonds. Report the photoelectron binding energy reference, reference lines, charge-compensation conditions and instrumental settings with the inferred chemical shift in photoelectron spectroscopy. A chemical interpretation should survive these checks as well as explain the line separation.

Sodium thiosulfate is the salt $\mathrm{N}{\mathrm{a}}_2{\mathrm{S}}_2{\mathrm{O}}_3$, often encountered as a hydrate. Its thiosulfate ion can participate in both oxidation-reduction reactions and metal-ion complex formation.

In photographic fixing, thiosulfate binds silver and helps dissolve residual silver halide. In analytical chemistry, reaction with iodine supports quantitative titration. These applications use different aspects of the same anion's chemistry.