About
Database
The PEPISCO database provides threshold photoelectron (TPE), photoion mass-selected threshold photoelectron (ms-TPE), photoelectron (PE) and photoionization (PI) spectra, to serve the valence photoionization community and users of vacuum ultraviolet beamlines around the globe. We compile experimental as well as simulated spectra with the goal to provide a compendium rich in metadata for photoionization experiments and analytical purposes.
The raw spectral data can be downloaded by clicking on the spectrum title. We are grateful for comments and corrections.
Some experimental spectra contain isomeric contributions in addition to that of the compound. Look for an exclamation mark in the spectrum title.
New contributions are much appreciated and will be included in the database promptly. There is a newly available tool PEPISCO entry for Windows and macOS. The macOS version is unsigned, if you have trouble installing it, please get in touch with us. Have fun! Before editing submitting data to pepisco@psi.ch, have a look at the user's manual: PEPISCO_entry.pdf. If you prefer not to start from scratch, download and have a look at the data set for formamide first!
Please cite the original publication of each spectrum. Furthermore, we would be grateful if you could also cite the Photoelectron Photoion Spectral Compendium (J. Phys. Chem. C 127, 34, 16751–16763, 2023, DOI: 10.1021/acs.jpcc.3c03120).
Version: 3.21, Date: 2026-02-27
Compiled and maintained by the Reaction Dynamics Group of the VUV beamline at Paul Scherrer Institute, 2023-2026,
with contributions from
Thomas Bierkandt,
Andras Bodi,
Myriam Drissi,
Gustavo Garcia-Macias,
Marius Gerlach,
Shane J. Goettl,
Patrick Hemberger,
Keisuke Kanayama,
Emil Karaev,
Ginny Karrir,
Zeyou Pan,
Minna Patanen,
Gaël Rouillé,
Mayank Saraswat,
Dorothee Schaffner,
Balint Sztaray,
Teissieres Titouan,
Xiangkun Wu, and
Zihao Zhang.
The yield of close-to-zero kinetic energy (threshold) electrons as a function of photon energy. Spectra may or may not be corrected for the photon flux.
The peak intensity of a given m/z channel in the threshold photoionization mass spectrum, or, in other words, the yield of close-to-zero kinetic energy (threshold) electrons detected in coincidence with a cation of a given m/z ratio, as a function of photon energy.
The yield of kinetic energy electrons collected at a fixed photon energy or a fixed electron kinetic energy, plotted as a function of the photon energy minus the electron kinetic energy.
The yield of slow electrons (up to a few tens of meV) as a function of photon energy, plotted by taking into account the electron kinetic energies. May also be photoion mass-selected (ms-SPES) when detected in coincidence with cations of a certain m/z ratio.
The peak intensity of a given m/z channel in the photoionization mass spectrum as a function of photon energy. Also called ion yield or, "incorrectly," photoion efficiency curve.
For a pure compound, the TPES corresponds to the sum of ms-TPES of its parent and fragment ions exactly, assuming 100% cation collection efficiency. The differences between the TPES and SPES are normally negligible, with SPES offering better signal-to-noise ratios all else being equal. The relative band intensities may be different in the PES, which also offers less resolution. The PIS often follows the integral of the (T)PES. However, this relationship is rather approximative and breaks down catastrophically (not quite like the K–T extinction, but still) in the presence of strong autoionization resonances.
Contact: pepisco@psi.ch