Two-photon resonant excitation of interatomic coulombic decay in neon dimers

The recent availability of intense and ultrashort extreme ultraviolet sources opens up the possibility of investigating ultrafast electronic relaxation processes in matter in an unprecedented regime. In this work we report on the observation of two-photon excitation of interatomic Coulombic decay (ICD) in neon dimers using the tunable intense pulses delivered by the free electron laser FERMI. The unique characteristics of FERMI (narrow bandwidth, spectral stability, and tunability) allow one to resonantly excite specific ionization pathways and to observe a clear signature of the ICD mechanism in the ratio of the ion yield created by Coulomb explosion. The present experimental results are explained by ab initio electronic structure and nuclear dynamics calculations

Interatomic Coulombic Decay Processes after Multiple Valence Excitations in Ne Clusters

We present a comprehensive analysis of autoionization processes in Ne clusters (~5000 atoms) after multiple valence excitations by free electron laser radiation. The evolution from 2-body interatomic Coulombic decay (ICD) to 3-body ICD is demonstrated when changing from surface to bulk Frenkel exciton excitation. Super Coster-Kronig type 2-body ICD is observed at Wannier exciton which quenches the main ICD channel

Slow interatomic Coulombic decay of multiply excited neon clusters

Ne clusters ( 3c5000 atoms) were resonantly excited (2p\u21923s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate

Post-compression of high-energy femtosecond pulses using gas ionization

We present a new optical post-compression technique designed for high-energy ultrashort pulses. A large spectral broadening is achieved through rapid ionization of helium by an intense pulse (> 1015 W/cm2) propagating in a capillary filled with low-pressure helium. The blueshifted pulses are re-compressed with chirped mirrors and silica plates. From a terawatt Ti:sapphire laser chain providing pulses of 40 fs, 70 mJ, we demonstrate the compression of pulses down to 11.4 fs (FWHM) with a total output energy of 13.7 mJ

Gas ionization induced post-compression of high energy and super-intense femtosecond pulses

From a 40 fs - 70 mJ terawatt Ti:sapphire laser, compression of pulses down to 11.4 fs (FWHM) with a total output energy of 13.7 mJ is achieved through, rapid ionization of helium

Characterizing ultrashort laser pulses by the rotational Doppler effect

International audienceTechnological advances in femtosecond laser sources call for the development of increasingly refined characterization tools implying to enrich the existing panel of operable nonlinear interactions. Toward that end, we have recently proposed a variant of SPIDER (spectral phase interferometry for direct electric field reconstruction) based on a nonstandard effect for producing the frequency shear, the so-called rotational Doppler effect. The method called DEER-SPIDER, for Doppler effect E-field replication, has the advantage of producing a spectral shearing at/near the fundamental wavelength, thus allowing operation in the ultraviolet spectral range. The present paper provides a deeper study of this approach. The method is tested under two different challenging conditions, and a thorough theoretical analysis is proposed. Possible improvements and an outlook are also discussed