Free, cross-platform XPS peak-fitting for macOS & Windows — with a built-in fit auditor and a citation-backed reference database. The modern replacement for XPSPEAK 4.1.
The alpine pika lives on rocky peaks — a fitting mascot for a peak-fitting tool. (Always one word: PikaXPS.)
PikaXPS reproduces the familiar XPSPEAK workflow with a modern interface, then goes further: it doesn't just let you fit X-ray photoelectron spectroscopy data — it checks whether your fit is physically and statistically defensible, and it knows the literature binding energies so you don't have to look them up.
Free and open source (GPLv3). Academic use is free forever. No account, no limits, no ads on the download — and no 5,000-point / 51-peak ceiling like XPSPEAK.
| PikaXPS | XPSPEAK 4.1 | CasaXPS | KherveFitting / LG4X | |
|---|---|---|---|---|
| Price | Free (OSS) | Free | €830+ (academic) | Free (OSS) |
| macOS native | ✅ | ❌ (Windows only) | ❌ (emulation) | ✅ |
| Built-in fit auditor | ✅ | ❌ | ❌ | ❌ |
| Citation-backed reference DB | ✅ | ❌ | partial | ❌ |
| One-click fitting recipes | ✅ | ❌ | ✅ | ❌ |
| Doublet + satellite peak types | ✅ | limited | ✅ | partial |
| Actively maintained | ✅ | ❌ (1999) | ✅ | ✅ |
- Backgrounds — Shirley (iterative), Shirley+Linear, Tougaard (U2), Linear, plus an active Shirley that co-fits with the peaks. Draggable endpoints; "Fit BG" settles the background first.
- Lineshapes — Gaussian-Lorentzian (sum & product), Voigt, exponential-tail asymmetric, Doniach-Šunjić for metals.
- Peak types — set each peak as single / doublet / satellite from the table. Doublets auto-constrain spin-orbit splitting, area ratio and FWHM; satellite areas are folded into the parent species for quantification.
- 🔍 Fit audit — a one-click report that checks FWHM sanity, binding energies against the reference DB, doublet integrity, metallic-lineshape asymmetry, expected satellites, over-fit signals, charge referencing, the residual (band-passed z-score), and a leave-one-out peak-necessity test (BIC) that flags peaks the data doesn't actually require.
- Reference database — 24 elements with binding energies, spin-orbit parameters and RSFs,
every value carrying its literature citation (Biesinger, Moulder, NIST SRD 20). One-click
recipes (Ni 2p, Co 2p, Fe 2p, C 1s, O 1s, S 2p, Pt 4f, Mo 3d, …). Add your own references —
saved to
~/.xpsfit/user_refdb.json, kept across updates. - Import —
.dat/.txt/.csv/.xlsx/.xls, Thermo Avantage multi-sheet exports, VAMAS.vms, or paste two columns straight from Excel/Origin. KE→BE conversion built in. - Quantification — Scofield-RSF atomic % (doublet/satellite areas summed automatically).
- Charge correction — pick the fitted C–C peak, shift every region to 284.8 eV in one click.
- Batch fitting, publication figures (PNG/SVG/PDF) and CSV/Excel export.
- Korean help built in (백그라운드/라인섀입/constraint/대전보정/정량 가이드, 출처 포함).
Download the latest signed build from the Releases page:
- macOS — unzip, move
PikaXPS.appto Applications, first launch via right-click → Open. - Windows — unzip, run
PikaXPS.exefrom the extracted folder ("More info → Run anyway" on the first SmartScreen prompt).
No Python install required.
git clone https://github.com/contact993/pikaxps && cd xpsfit
python -m venv .venv && . .venv/bin/activate
pip install -e .
python -m xpsfit.appThis tool grows from its users:
- Bug / feature — open an issue.
- Questions & feature voting — the Discussions board.
- 📚 Contribute a reference value — use the Submit a reference value issue template (a literature source is required). Accepted submissions ship in the next release with credit, so the database keeps getting richer.
If PikaXPS helped your work, please cite it (see CITATION.cff). A software paper with a DOI is in preparation; until then, cite the repository and release version.
GPLv3 (see LICENSE). Academic and non-commercial use is free, forever. Commercial use is currently also free under the GPLv3 until a commercial license is established — see COMMERCIAL-LICENSE.md. Third-party components and reference-data sources are listed in THIRD-PARTY-LICENSES.txt.
Maintained part-time by a single developer. Released as stable open source: if updates slow, the tool remains usable and the source stays available. Reference-data values are literature starting points — always verify assignments against the cited sources before publication.
M. C. Biesinger et al. (Appl. Surf. Sci. 2010/2011; Surf. Interface Anal. 2009) · J. F. Moulder et al., Handbook of XPS (1992) · NIST XPS Database SRD 20 · J. H. Scofield (1976) RSFs.