Experimental Technique

Synchrotron Vacuum Ultraviolet Photoionzation Mass Spectrometry

The synchrotron Vacuum Ultraviolet photoionization–high-resolution time-of-flight mass spectrometry (SVUV-PI-TOFMS) method combines the advantages of synchrotron radiation (high brilliance and wavelength tunability), in situ online ultrasonic molecular beam sampling, and the rapid, highly sensitive detection capabilities of time-of-flight mass spectrometry. It enables near-threshold ionization and non-discriminatory analysis against polarity for gas-phase reaction products, thereby allowing the detection of key radical intermediates in energy conversion processes, distinction of isomers, and analysis of complex product compositions. This makes it highly suitable for investigating critical scientific questions in energy conversion research.

Beamline optics

Overview

The Energy Conversion and Astrochemistry Photoionization Mass Spectrometry Beamline comprises two branches: a white light branch (WB) and a monochromator branch (MB). The white light branch utilizes an undulator for monochromatization, delivering high-flux white light beams to Experimental Station 1. The monochromator branch employs gratings for monochromatization, providing monochromatic light to Experimental Stations 2 and 3, with two plane variable-line-spacing gratings installed to accommodate different experimental requirements. The two branches are switched via the deflection mirror M0 and operate on a time-sharing basis. A Monk-Gillieson (MG) monochromator design is adopted. M2 serves as the pre-focusing mirror of the monochromator, and G is the plane variable-line-spacing grating. Together, they form the MG monochromator. During wavelength scanning, only the rotation of the grating axis is required, resulting in a simple structure. This system features a straightforward design and, when coupled with an Undulator light source, directly uses the source as the entrance slit, facilitating high throughput.

Key Performance

Experimental Endstation

A-Branch: Astrochemistry

The Astrochemistry Endstation is capable of simulating interstellar environments under cryogenic ultra-high vacuum conditions. By combining high-performance synchrotron radiation and high-resolution mass spectrometry with true in-situ online ionization, it reduces ion transmission losses and enhances the detection capability for trace radicals and reaction intermediates. The system consists of a sample introduction system, a high-energy electron irradiation system, a reaction chamber, and a detection system. It can simulate interstellar conditions at ultra-high vacuum (10-8 Pa) and ultra-low temperatures (5 K), providing experimental support for astrochemical kinetics studies and opening new possibilities for exploring the origins of the universe and even life itself.

Experimental station layout

Key Performance

B-Branch: Combustion

Combustion Endstation is dedicated to investigating the combustion process, encompassing fuel pyrolysis, oxidation, and combustion reactions. The station employs vacuum ultraviolet (VUV) light with an energy range of 5 eV to 20 eV, which enables the ionization of nearly all combustion products. A novel gas filter system ensures the provision of high-purity VUV light. A custom-built time-of-flight mass spectrometer, offering a mass resolution of 3000 and a detection limit of 0.1 ppm, is used to analyze combustion reaction products. These include key intermediates such as radicals, hydroperoxides, and aromatics, as well as final combustion products. By tuning the VUV photon energy, photoionization efficiency spectra can be acquired, facilitating the identification of molecular structures—particularly distinguishing between isomers. The station is equipped with combustion reactors capable of operating across temperature ranges from 300 K to 2000 K and pressures from 0.001 atm to 10 atm.

Experimental station layout

Key Performance

B-Branch:  Catalysis

Key Performance

Overview

MB-ES3 is a catalysis endstation with the VUV beam energy ranging from 5 eV to 20 eV. Equipped with a high resolution time-of-flight mas spectrometer as detector, this endstation is designed to capture the fleeting intermediates during catalytic reactions.

I. Catalytic reactor 

  The catalytic reactor is designed to be coupled with PIMS to in situ capture the fleeting intermediates during catalytic reactions.

   Thermal catalytic reactor: pressure up to 20 bar, temperature up to 1000 K;

   Photocatalytic reactor

II. Photoionization mass spectrometer

    Mass range: 2~300 amu;

    Mass resolution: >5000@m/z 128;

    Mass error: < 20 ppm;

    Dynamic range: 5 orders of magnitude;

    Limit of detection: ~ 0.1 ppm

III. Auxiliary Equipment

   Mass flow controller;

   Temperature controller;

   Hydrogen generator;　

Science

Scientific Scope 1: Astrochemistry plays a key role in interpreting astronomical spectra and simulating reaction mechanisms, thereby validating observations. The detection of complex organic molecules (COMs)—such as aldehydes, ketones, acids, and amino acids—provides tracers for studying physical and chemical conditions in star-forming regions. Over 200 molecular species have been confirmed in interstellar space, with many more awaiting identification. Additionally, meteorites containing carboxylic acids, amino acids, and ribose offer clues to the origin of life, as they may have delivered prebiotic materials to early Earth. Investigating the formation mechanisms of extraterrestrial organic molecules with the utilization of SVUV-PIMS technology is significant to astrochemistry, astrobiology, and the study of galactic evolution and life’s origins.

Scientific Scope 2： The primary scientific objective of the combustion station is to develop combustion reactors that simulate the combustion processes occurring in aircraft engines, ramjets, cryogenic liquid rocket engines, and solid-propellant missiles, with a particular emphasis on combustion chemistry across broad temperature and pressure ranges. To achieve this goal, the station investigates the pyrolysis, oxidation, and combustion of various fuels, including sustainable aviation fuels, high-energy-density aviation fuels, energetic materials, ionic liquid rocket propellants, as well as liquid hydrogen and methane. Based on the detailed experimental data obtained, both comprehensive and simplified reaction mechanisms for these fuels will be developed and utilized to simulate engine combustion processes. These studies are essential for advancing new fuel formulations and optimizing combustion engines towards higher efficiency and lower emissions.

Scientific Scope 3： Increasing the sensitivity and mass resolution of photoionization mass spectrometry enables the in-situ detection of trace and fleeting reactive intermediates such as ketene, radical, carbene et al. during catalytic reactions. This capability is critical for the determination of key reaction steps and elucidation of reaction network during the catalytic reaction, including thermal catalytic and photocatalytic reactions. The reactions include syngas to olefins, oxidative coupling of methane, methane to aromatics, methanol to hydrocarbons, oxidative dehydrogenation of propane, methane dry reforming, catalytic recycling of plastics et al..

People

Useful Link

Related beamlines:

ALS-Chemical Transformations (Vacuum Ultraviolet) beamline:

https://als.lbl.gov/beamlines/9-0-2/

SLS-Vacuum Ultraviolet Radiation beamline:

https://www.psi.ch/en/sls/vuv

SOLEIL-DESIRS beamline:

https://www.synchrotron-soleil.fr/en/beamlines/desirs