arXiv subjects

P. Rosenberger

Publications and source records attributed to P. Rosenberger.

5 recordsLinked to original sources

arXiv2025

Relaxation dynamics in excited helium nanodroplets probed with high resolution, time-resolved photoelectron spectroscopy

Superfluid helium nanodroplets are often considered as transparent and chemically inert nanometer-sized cryo-matrices for high-resolution or time-resolved spectroscopy of embedded molecules and clusters. On the other hand, when the helium nanodroplets are resonantly excited with XUV radiation, a multitude of ultrafast processes are initiated, such as relaxation into metastable states, formation of nanoscopic bubbles or excimers, and autoionization channels generating low-energy free electrons. Here, we discuss the full spectrum of ultrafast relaxation processes observed when helium nanodroplets are electronically excited. In particular, we perform an in-depth study of the relaxation dynamics occurring in the lowest 1s2s and 1s2p droplet bands using high resolution, time-resolved photoelectron spectroscopy. The simplified excitation scheme and improved resolution allow us to identify the relaxation into metastable triplet and excimer states even when exciting below the droplets' autoionization threshold, unobserved in previous studies.

physics.atm-clus↗

arXiv2021

Onset of space-charge effects in strong-field photocurrents from nanometric needle tips

Strong-field photoemission from nanostructures and the associated temporally modulated currents play a key role in the development of ultrafast vacuum optoelectronics. Optical light fields could push their operation bandwidth into the petahertz domain. A critical aspect for their functionality in the context of applications is the role of charge interactions, including space charge effects. Here, we investigated the photoemission and photocurrents from nanometric tungsten needle tips exposed to carrier-envelope phase-controlled few-cycle laser fields. We report a characteristic step-wise increase in the intensity-rescaled cutoff energies of emitted electrons beyond a certain intensity value. By comparison with simulations, we identify this feature as the onset of charge-interaction dominated photoemission dynamics. Our results are anticipated to be relevant also for the strong-field photoemission from other nanostructures, including photoemission from plasmonic nano-bowtie antennas used in carrier-envelope phase-detection and for PHz-scale devices.

physics.optics↗

arXiv2021

Single-shot Dispersion Sampling for Optical Pulse Reconstruction

We present a novel approach to single-shot characterization of the spectral phase of broadband laser pulses. Our method is inexpensive, insensitive to alignment and combines the simplicity and robustness of the dispersion scan technique, that does not require spatio-temporal pulse overlap, with the advantages of single-shot pulse characterization methods such as single-shot frequency-resolved optical gating at a real-time reconstruction rate of several Hz.

physics.optics↗

arXiv2019

Single-shot carrier-envelope-phase measurement in ambient air

The ability to measure and control the carrier envelope phase (CEP) of few-cycle laser pulses is of paramount importance for both frequency metrology and attosecond science. Here, we present a phase meter relying on the CEP-dependent photocurrents induced by circularly polarized few-cycle pulses focused between electrodes in ambient air. The new device facilitates compact single-shot, CEP measurements under ambient conditions and promises CEP tagging at repetition rates orders of magnitude higher than most conventional CEP detection schemes as well as straightforward implementation at longer wavelengths.

physics.optics↗

arXiv2019

CEP-Controlled Molecular Dissociation by Ultrashort Chirped Laser Pulses

We demonstrate and characterize that a carrier-envelope-phase (CEP)-controlled ultrashortchirped field is an efficient and robust mechanism to modify the dissociation dynamics of molecularhydrogen. Different dissociation pathways are collectively induced and their interference contributeto the kinetic energy release spectra. Chirping is able to efficiently manipulate the interferencesof different dissociation pathways. We demonstrate a linear relationship between chirp and CEP-dependence, dissociation as well as directional electron localization.

physics.atom-ph↗