A velocity map imaging spectrometer for electron–ion and ion–ion coincidence experiments with synchrotron radiation

Rolles, Daniel; Pešić, Z. D.; Perri, Mark J.; Bilodeau, R. C.; Ackerman, G. D.; Rude, B.; Kilcoyne, A. L. D.; Bozek, John D.; Berrah, N.

doi:10.1016/j.nimb.2007.04.186

Cited by 46 publications

(25 citation statements)

References 16 publications

(18 reference statements)

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“…The ions were detected at the 30 Hz LCLS beam rate in a standard ion time-of-flight (iToF) apparatus [17,18] that was usually operated in Wiley-McLaren configuration with a ~150V/cm extraction field. The iToF extractor electrode contained a 1 x 10 mm slit oriented orthogonal to the incident x-ray direction.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Time-resolved pump-probe experiments at the LCLS

et al. 2010

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Abstract:The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-rayinduced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs. ©2010 Optical Society of America

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Section: Experiments and Resultsmentioning

confidence: 99%

Time-resolved pump-probe experiments at the LCLS

et al. 2010

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“…In coincidence methods, each event is analyzed separately, tracing back the detected ions to a single source-an ionized and subsequently dissociating molecule, cluster, or nanoparticle. By its nature, it is one of the most accurate approaches in experimentally reconstructing the quantum mechanical event [25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics of XFEL-Induced Photo-Dissociation, Revealed by Ion-Ion Coincidence Measurements

et al. 2017

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X-ray free electron lasers (XFELs) providing ultrashort intense pulses of X-rays have proven to be excellent tools to investigate the dynamics of radiation-induced dissociation and charge redistribution in molecules and nanoparticles. Coincidence techniques, in particular multi-ion time-of-flight (TOF) coincident experiments, can provide detailed information on the photoabsorption, charge generation, and Coulomb explosion events. Here we review several such recent experiments performed at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan, with iodomethane, diiodomethane, and 5-iodouracil as targets. We demonstrate how to utilize the momentum-resolving capabilities of the ion TOF spectrometers to resolve and filter the coincidence data and extract various information essential in understanding the time evolution of the processes induced by the XFEL pulses.

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“…VMI can provide angle and energy resolved photo-ion and photo-electron spectra in a simple, economical setup without the requirement for extensive post acquisition analysis except an inversion procedure that can be achieved in a few different ways [9][10][11][12] . Since the time it was first introduced, VMI has evolved and has been modified and improved, for example, to obtain three dimensional velocity distributions using time-slicing [13][14][15] , to image ions and electrons in coincidence 16,17 for a complete reconstruction of a photon-molecule interaction event, etc.…”

Section: Velocity Map Imaging (Vmi)mentioning

confidence: 99%

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

Shivaram

Champenois

Cryan

et al. 2016

Applied Physics Letters

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We demonstrate a new technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. This spatial gating in velocity map imaging can benefit nearly all photoion pump-probe VMI experiments especially when extreme-ultraviolet (XUV) light or X-rays are involved which produce large background signals on their own. Velocity Map Imaging (VMI)1,2 is a technique for imaging charged particles which is now widely used in atomic, molecular and chemical physics experiments to study a variety of different processes in gas phase systems. It has become a standard technique to measure ultrafast processes in these systems on attosecond and femtosecond time scales using vacuum-ultraviolet (VUV) and extreme-ultraviolet (XUV) light from high-order harmonic generation (HHG) and Free Electron Laser (FEL) sources 3-7 , and to study X-ray driven processes from synchrotron sources 8 . VMI can provide angle and energy resolved photo-ion and photo-electron spectra in a simple, economical setup without the requirement for extensive post acquisition analysis except an inversion procedure that can be achieved in a few different ways 9-12 . Since the time it was first introduced, VMI has evolved and has been modified and improved, for example, to obtain three dimensional velocity distributions using time-slicing 13-15 , to image ions and electrons in coincidence 16,17 for a complete reconstruction of a photon-molecule interaction event, etc.Here, we present a new technique which involves a simple modification of the input laser beam geometry in a standard VMI which results in significant enhancement of signal-to-noise ratio in time resolved pump-probe measurements. In typical pump-probe experiments using VMI, the pump and probe laser beams are focused on a gas target at the center of the VMI setup where they are temporally and spatially overlapped. The laser beams propagate along a line parallel to the VMI electrodes and the charged particles born along this line are a) Electronic mail: nhshivaram@lbl.gov imaged by the VMI spectrometer. Since these particles are born at the same distance from the repeller electrode, their time-of-flight to the detector for a given mass is the same irrespective of distance along the laser propagation direction. In our method, we make a simple modification of this standard beam geometry by introducing a tilt in the laser beams propagating through the VMI setup (see Fig. 1). This is effectively a 'passive streaking' of the particles which creates a variation in time-of-fl...

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A velocity map imaging spectrometer for electron–ion and ion–ion coincidence experiments with synchrotron radiation

Cited by 46 publications

References 16 publications

Time-resolved pump-probe experiments at the LCLS

Time-resolved pump-probe experiments at the LCLS

Molecular Dynamics of XFEL-Induced Photo-Dissociation, Revealed by Ion-Ion Coincidence Measurements

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

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