Beamline description

MOST aims to provide high flux in a wide photon energy range: 9-2200 eV; high spectral resolution: better than 5000 in the almost spectral range; high spectral purity; full polarization  control; transmission almost indipendent from the input polarization.
MOST will consist of 2 lines after the first optical elements: a) PM0 first optical element: plane mirror, 0.75° grazing incidence, common to both HE and LE branches. and  b) tSWM switching mirror, out or 2° :

1.  a branch line for the low energy range (9-300) eV that will inherit the actual GasPhase optical setup and will operate with LEU;
2.  a new main line aiming to cover the wide range 15-2200 eV operated with both LEU and HEU. 

The undulators

The beamline receives light from two elliptically polarized undulators, covering the low/intermediate and intermediate/high photon energy range. Both undulators will allow a full control of the incoming light polarization.
LEU and HEU provide two sources that are separated by 2.4 m.

•  Low-Energy Undulator: LEU:  (APU: Adjustable Phase Undulator, fixed gap)
-     Photon energy range: 9 eV - 250 eV (H1, 2GeV)
-     Period length = 132 mm, number of periods = 18

•     High-Energy Undulator HEU (EPU: Elliptically Polarizing Undulator)
-     Photon energy range: 84 eV - 700 eV (H1, 2 GeV); up to 3 keV (H5, 2.4 GeV)
-     Period length = 50.36 mm, number of periods = 28

HE - MOST (main line)

The optical design of the main line monochromator of MOST aims to provide the highest possible performances given the light source and to take full advantage of the improved Elettra 2.0 storage ring operated at 2.4 GeV. 


A full description of the monochromator can be found in the Frassetto_et_al_2025.

LE - MOST (branch line)

The monochromator of the branch line is a modification of the GasPhase one. 

The main differences are:

MOST - BL instrumentations & infos

Differently from most other beamlines at ELETTRA, there is not a permanent end station at MOST. Our beamline is presently equipped with many distinct interchangeable apparatuses, listed below. Any apparatus is available to Users for their proposals, the choice of the end station depending on experimental requirements.

Moreover Users can bring their own apparatus to perform experiments, provided that it is compatible with beamline requirements (please contact beamline staff to check).

photoemission experiments on aggressive molecular species (radicals, transients, reactive species)

1. VG-220i set up for photoemission experiments on condensable vapours, also equipped for TOF mass spectrometry
2. Multi-coincidence experiments set up, for angle resolved and electron-electron coincidence experiments in a versatile multichannel configuration.
3. Molecular beam set up, for PEPICo mass spectroscopy
4. Velocity Map Imaging (VMI) 
5. PIFS, Photon Induced Fluorescence Spectroscopy (UV-Vis dispersed fluorescence with Minuteman 305V Czerny-Turner 0,5 m Spectrometer) 
6. ARPES-TPES, angle-resolved photoemission experiments on aggressive molecular species (radicals, transients, reactive species)
7. Two colors experiments SR + IR laser beam.
8. Absolute absorption cross section cell 

Two colors experiments SR + IR laser beam can be performed with set up 1 to 5 on the low energy branch line.

1.  SES200-ULLA, for high resolution photoemission of molecular vapours (LTP 20115157, prof. Carla Puglia, University of Uppsala, Sweden) [doi: 10.1063/1.4907723];
2. PIFS+ "XUV-PIK”, for dispersed emission experiments with a compact XUV spectrometer (LTP 20130233, dr. Luca Poletto, IFN-CNR, Padua, Italy) [doi: 10.1063/1.4898315];
3. “CESyRa”, for photoionization  of clusters of refractory materials, via electron-ion multicoincidence detection. (LTP 20170487; prof. Paolo Piseri, CIMAINA, University of Milan, Italy [on going upgrade; doi: 10.1016/j.elspec.2008.05.003]

Moreover each user can bring his own apparatus to perform experiments, provided that it is compatible with the beamline requirements (please contact beamline staff to check).

Experimental Facilities

• He lamp.
• Gas line with precision leak valves.
• UV-Vis monochromator
• Absolute absorption cross section cell