Spatially resolved measurements of the magnetization dynamics on a thin CoFeB film induced by an intense laser pump-pulse reveal that the frequencies of resulting spin-wave modes depend strongly on the distance to the pump center. This can be attributed to a laser generated temperature profile. We determine a shift of 0.5 GHz in the spin-wave frequency due to the spatial thermal profile induced by the femtosecond pump pulse that persists for up to one nanosecond. Similar experiments are presented for a magnonic crystal composed of a CoFeB-film based antidot lattice with a Damon Eshbach mode at the Brillouin zone boundary and its consequences are discussed.

In order to utilize the high repetition rates now available at X-ray free-electron laser sources for serial crystallography, methods must be developed to softly deliver large numbers of individual microcrystals at high repetition rates and high speeds. Picosecond infrared laser (PIRL) pulses, operating under desorption by impulsive vibrational excitation (DIVE) conditions, selectively excite the OH vibrational stretch of water to directly propel the excited volume at high speed with minimized heating effects, nucleation formation or cavitationinduced shock waves, leaving the analytes intact and undamaged. The soft nature and laser-based sampling flexibility provided by the technique make the PIRL system an interesting crystal delivery approach for serial crystallography. This paper demonstrates that protein crystals extracted directly from aqueous buffer solution via PIRL-DIVE ablation retain their diffractive properties and can be usefully exploited for structure determination at synchrotron sources. The remaining steps to implement the technology for high-speed serial femtosecond crystallography, such as single-crystal localization, high-speed sampling and synchronization, are described. This proof-of-principle experiment demonstrates the viability of a new laser-based high-speed crystal delivery system without the need for liquid-jet injectors or fixed-target mounting solutions

The benzyltriphenylphosphonium (BTP) thermometer ion is utilized to characterize the fragmentation mechanisms of matrix-assisted laser desorption/ionization (MALDI) for femtosecond ultraviolet laser pulses. We demonstrate that the survival yield of BTP approaches unity under these conditions, which suggests that a minimal amount of fragmentation is occurring. It is also shown that the survival yield of BTP is insensitive to the laser fluence. However, the magnitude of fragmentation for the matrix increased notably for the same fluence range. These results indicate that the amount of energy transferred from the matrix ions to the BTP thermometer ions is minimal because the femtosecond desorption applied here occur within the stress-confinement regime. This observation is in agreement with recent molecular dynamics simulations which predict that it should be possible to separate both desorption and ionization processes in the regime of stress-confined desorption. Our results indicate that angiotensin is the largest biomolecule which could be routinely measured with these pulses. A mass upper-limit supports the hypothesis that ionization is hindered by the increased thermal gradients imposed in the lattice and associated velocity distribution within the ablation process from the much higher lattice heating rate with femtosecond pulses. This effect results in the temporal overlap between the neutral molecules and the matrix ions being too small to result in sufficient proton exchange for ionization. Graphical TOC Entry2

Material ablation and evaporation using pulsed infrared lasers pose promising approaches for matrix-free laser desorption ionization and in laser surgery. For the best results, key parameters such as laser wavelength, pulse duration, and pulse energy need to be carefully adjusted to the application. We characterize the dynamics at the water-air interface induced by a 10 ps infrared laser tuned to the water absorption band at 3 lm, a parameter set facilitating stress confined desorption for typical absorption depths in biological samples and tissue. By driving the ablation faster than nucleation growth, cavitation induced sample damage during the ablation process can be mitigated. The resultant explosive ablation process leads to a shock front expansion and material ejection which we capture using off-axis digital interference microscopy, an interference technique particularly useful for detecting the phase shift caused by transparent objects. It is demonstrated that the method can yield local density information of the observed shock front with a single image acquisition as compared to the usually performed fit of the velocity extracted from several consecutive snapshots. We determine the ablation threshold to be ð0:560:2Þ J cm À2 and observe a significant distortion of the central parts of the primary shock wave above approximately 2:5 J cm À2. The differences in plume shape observed for higher fluences are reflected in an analysis based on shock wave theory, which shows a very fast initial expansion.