TMO Early Science

Early Science in Run 22 (IP2)

In addition to restarting User operations and offering Users the first opportunity to make use of the new LCLS-II superconducting accelerator, the TMO team will continue to develop and commission new capabilities to make them available for Users. In Run 22 we plan to continue the development of the angle-resolving electron ToF spectrometer (MRCO) which will be installed in IP1 for the latter part of Run 22. The TMO team will also work on installation and commissioning of the reaction microscope end station (DREAM) at IP2. Following these technical commissioning efforts, we will conduct ‘Early Science' experiments. This effort will be organized and led by LCLS staff (AMO and Chemical Sciences Departments). These plans will include interested members of the user community. These Early Science programs are intended to be pilot experiments that bridge between technical commissioning and regular user operations. MRCO is expected to be ready for User operations in the latter half of Run 22, whereas DREAM is expected to be ready in Run 23. 

If you are interested in participating in the Early Science programs in Run 22 (or for further information) please send a brief letter of interest by the Run 22 proposal deadline to:
James Cryan (jcryan@slac.stanford.edu) LCLS AMO Science Dept. Head, or
Thomas Wolf (thomas.wolf@slac.stanford.edu) LCLS Chemical Science Dept. Head
If you have already provided a letter of intent for the MRCO or DREAM effort in the Run 21 solicitation, do not feel you need to re-send the information, we have kept these previous submissions.

The AMOS department will be organizing a workshop for the User community to discuss DREAM Early Science in the summer of 2023. Further details will be posted once the workshop format is better understood. 

Early Science in Run 21 (IP1)

Following technical commissioning in Run 21, a period of ‘Early Science’ with the TMO instrument will be organized and led by LCLS staff (AMO and Chemical Sciences Departments). These plans will include interested members of the user community. These Early Science programs are intended to be pilot experiments that bridge between technical commissioning and regular user operations.

The LCLS Staff (along with the User community) have developed the following Early Science program for Run 21:

• Investigating Ultrafast Intersystem Crossing in Organic Push-Pull Molecules with X-ray Absorption: We will probe the ultrafast intersystem crossing dynamics in 4-nitro-1-napthylamine following 400 nm excitation. We will make use of time-resolved X-ray absorption spectroscopy at both the nitrogen and oxygen K-edges which has been demonstrated sensitivity of trXAS to the electronic character of a populated excited state, specifically nπ* states.
• Dynamics of Core-Excited States probed by X-ray Observables: We propose to use time-resolved soft x-ray photoelectron spectroscopy (trXPS) with attosecond pump and attosecond probe pulses to study the coherent electronic dynamics near conical intersections in core-excited systems. Although CI dynamics have been studied in several previous studies, predictions of coherent electronic phenomena have yet to be verified experimentally. As a consequence, the predicted influence of electronic coherence on CI dynamics and the possibility to control CI dynamics on the electronic time scale have remained elusive.

Previous Early Science (Run18)

The new designed Time-resolved atomic, Molecular and Optical science (TMO) instrument, began RUN 18 with Early Science Experiments which were open to the community. The Early Science was lead by Ming-Fu Lin, James Cryan and Peter Walter with the expectation of strong participation from key members of the AMO community. 

The following Early Science Experiments were scheduled:

• LW05 - High Field Physics at TMO: To finalize the transition from commissioning to operation, we have foreseen High Field Physics (HFP) experiments. With the new hardware TMO will reach irradiation levels around 10^19 W/cm². Compared to previous efforts on this topic, this opens new routes to characterizing highly transient ionic atomic and molecular systems. We propose to perform resonant double core hole (DCH) studies in Ne and N2O. This will capitalize on scientific results that LCLS enabled in 2009, i.e. DCH spectroscopy on atomic systems, benchmark the irradiation achieved under the new conditions and then expand the Resonant-DCH scheme to molecules. Concluding we will perform non-sequential ionization experiments by investigating two photon absorption and two photon non-sequential double ionization in Ne.​
• LW06 - Chemical Dynamics in Ultrafast Molecular Dissociation Of Nitrous Oxide: The aim of the proposed experiment is to monitor fundamental chemical processes at their inherent time scale from a few to tens of femtoseconds, not only resolving the energy but also the symmetry evolution of electron orbitals. We seek to directly and site-specifically reveal ultrafast chemical dynamics during molecular restructuring of the atmospherically important nitrous oxide (N2O). Therefore, we plan to efficiently dissociate N2O with an X-ray pulse at 430 eV followed by another time shifted X-ray pulse at 440 eV which monitors the chemical (spectral) changes with femtosecond resolution via investigation of the K-Shell photoelectron emission with angular resolution. ​
• LW08 - UV-driven Photochemistry in NO2: NO2​ is well-known to photodissociate upon excitation <400 nm. After photoexcitation to the A state, it relaxes within 200 fs through a conical intersection back to its ground state mainly through O-N-O bending. It undergoes ON-O dissociation in the ground state within <1 ps. The dissociating molecules should localize almost all of the photoabsorbed energy in their asymmetric stretch degree of freedom. We will investigate the coherent nature of this dissociation process with time-resolved x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) from total ion yield measurements at the nitrogen and oxygen K-edges. Both methods can be expected to be sensitive to bond dissociation processes. This experiment will demonstrate our readiness to perform time-resolved photochemistry experiments in advance of User experiments. ​
• LW07 Channel Coupling in Attosecond Photoemission: Many-electron correlations, relativistic effects, and relaxation effects of the ionic core in the ionization process need to be taken into account when considering ionization on the attosecond timescale. We propose to use angular streaking of Xenon 3d photoelectrons (3d5​/2​: Ip​​ = 677 eV, 3d3​/2​: Ip​​ =  689 eV). Calculation and measurements show interesting features in the 3d-subshell photoionization cross section and anisotropy parameters. The 3d-subshell electrons show channel coupling features, i.e. electron correlation effects, that cause interaction between the two continuum channels. In the cross sections, these show up as a second resonance in the 3d5​/2​ cross-section corresponding to the 3d3​/2​ ionization potential. We propose to measure the relative delay between the two lines in the 3d-doublet, and fully characterize the measured electron wavepackets using the reconstruction technique developed and experimentally demonstrated in experiments before. This provides a measurement to help resolve electron correlation effects with attosecond precision.