Generation of ultra-short hydrogen atom pulses by bunch-compression photolysis

Abstract

Ultra-short light pulses enable many time-resolved studies in chemistry, especially when used in pump-probe experiments. However, most chemical events are not initiated by light, but rather by collisions. Time-resolved collisional experiments require ultra-short pulses of atoms and molecules-sadly, methods for producing such pulses are so far unknown. Here we introduce bunch-compression photolysis, an approach to forming ultra-short and highly intense pulses of neutral atoms. We demonstrate H-atom pulses of 1.2±0.3 ns duration, far shorter than any previously reported. Owing to its extraordinarily simple physical principles, we can accurately model the method-the model shows H-atom pulses as short as 110-ps are achievable. Importantly, due to the bunch-compression, large (mm 3 ) photolysis volumes are possible, a key advantage for pulse intensity. This technique overcomes the most challenging barrier to a new class of experiments on time-resolved collisions involving atoms and molecules.

Laser Sculpting of Atomic sp, sp2, and sp3 Hybrid Orbitals

“…The possibility of achieving this task experimentally is supported by recent progress in control of delay times, not only in the attosecond but even in the zeptosecond time domain (1 zsec = 10 À21 s). [34] Focusing the series of laser pulses on the H atoms in the laser spot during 1 ps will profit from the development of a new generation of H-atomic beams, [35] with 100 to 1000 times better resolution than can be achieved with traditional technology. [36,37]…”

“…The laser parameters of the first and third laser pulses are more challenging, but this task may be mastered for example, by means of the techniques that have been developed by H. C. Kapteyn, M. M. Murnane, and co-workers. [34] Focusing the series of laser pulses on the H atoms in the laser spot during 1 ps will profit from the development of a new generation of H-atomic beams, [35] with 100 to 1000 times better resolution than can be achieved with traditional technology. [33] Furthermore, the present approach calls for control of the time delay Dt (see Figure 1a).…”

An ultrahigh vacuum apparatus for H atom scattering from surfaces

“…[32][33][34][35] Currently, we are working on the realization of a short pulse version to perform pump-probe experiments with a H atom beam in combination with an ultra-short laser pulse. 36 Furthermore, we want to expand the source concept for atomic…”

Inelastic Scattering of H Atoms from Surfaces

“…Pump–probe style experiments with ultrashort (∼100 ps) H atom pulses is another idea that emerged in our laboratory some years ago. 174 A new machine based on this idea is now operating in Göttingen, with which one can study H atom scattering from laser-excited surfaces. Finally, photolysis can be extended to other atoms of the periodic table—C, O, and N atoms—by photolysis of diatomic molecules like O 2 , NO, and CO using VUV light from a free electron laser.…”