Resonance-enhanced three-photon single ionization of Ne by ultrashort extreme-ultraviolet pulses

Eiji Shigemasa,Lisa Ishikawa (Okihara),James R Harries,Hiroshi Iwayama,Mitsuru Nagasono

doi:10.1088/0953-4075/46/16/164020

Abstract

Time-resolved extreme-ultraviolet (EUV) fluorescence spectroscopy has been applied to study the multi-photon, single ionization of Ne irradiated by intense EUV-free-electron laser (FEL) pulses at a wavelength of 51 nm. A broad, intense peak at a wavelength of around 46 nm is observed, which is shorter than the incident FEL wavelength. The time dependence of the fluorescence reveals that the peak has two unresolved components, which we attribute to the decay of the excited ion states Ne+ 2s−1(2S) and 2p−2(3Pe)3s(2Pe) at 46.0 and 44.6 nm. From the observed intensity ratios and fluorescence lifetimes we conclude that the Ne+ 2p−2(3Pe)3s(2Pe) state is populated by two-photon resonance enhancement, via a 2p43p2 doubly excited state of Ne.

Highlights

With the advent of free-electron laser (FEL) facilities operating at wavelengths ranging from the extreme ultraviolet (EUV) to x-rays, we are undoubtedly entering a new age of photoscience
The FEL radiation was linearly polarized in the horizontal direction, and the repetition rate was 30 Hz
The EUVFEL pulses are transported using a pair of flat mirrors in the accelerator tunnel to the experimental hall and focused with a pair of elliptical and cylindrical mirrors [18]

Summary

Introduction

With the advent of free-electron laser (FEL) facilities operating at wavelengths ranging from the extreme ultraviolet (EUV) to x-rays, we are undoubtedly entering a new age of photoscience. In the research field of atomic and molecular physics, nonlinear processes such as multi-photon absorption have become a major target to be investigated in the short wavelength region [1,2,3,4,5,6,7,8,9]. The modelling of nonlinear interactions of short-wavelength and short-pulse radiation with matter is essential for a wide range of basic and applied research, and there is a strong demand for understanding

Present address

Experiment

Summary