Fluorescence intensity correlation imaging with high spatial resolution and elemental contrast using intense x-ray pulses.

Phay J Ho,Linda Young,Christopher Knight

doi:10.1063/4.0000105

Abstract

We theoretically investigate the fluorescence intensity correlation (FIC) of Ar clusters and Mo-doped iron oxide nanoparticles subjected to intense, femtosecond, and sub-femtosecond x-ray free-electron laser pulses for high-resolution and elemental contrast imaging. We present the FIC of and emission in Ar clusters and discuss the impact of sample damage on retrieving high-resolution structural information and compare the obtained structural information with those from the coherent diffractive imaging (CDI) approach. We found that, while sub-femtosecond pulses will substantially benefit the CDI approach, few-femtosecond pulses may be sufficient for achieving high-resolution information with the FIC. Furthermore, we show that the fluorescence intensity correlation computed from the fluorescence of the Mo atoms in Mo-doped iron oxide nanoparticles can be used to image dopant distributions in the nonresonant regime.

Highlights

Coherent diffractive imaging (CDI)[1,2] with x-ray free-electron laser (XFEL) pulses holds the promise to probe the structure[3,4] and follow the dynamics[5,6,7] of entities with atomic resolution.[1]
We theoretically investigate the fluorescence intensity correlation (FIC) of Ar clusters and Mo-doped iron oxide nanoparticles subjected to intense, femtosecond, and sub-femtosecond x-ray free-electron laser pulses for high-resolution and elemental contrast imaging
We begin our discussion by showing the fluorescence intensity and the FIC associated with the Ka and Kah channels of Ar1415 and Ar149171 subjected to an intense 2 fs pulse

Summary

Introduction

Coherent diffractive imaging (CDI)[1,2] with x-ray free-electron laser (XFEL) pulses holds the promise to probe the structure[3,4] and follow the dynamics[5,6,7] of entities with atomic resolution.[1]. The idea is that with short-duration pulses, high-resolution diffraction patterns can be captured with a single XFEL pulse before the system of interest suffers damage from the intense radiation.[1] Despite continuous progress, it has remained a challenge[8,9] to achieve nanometer or subnanometer resolution and elemental contrast[10] with CDI This is because intense x-ray pulses will lead to extremely rapid structural degradation of the sample and generate a large number of delocalized electrons, resulting in a substantial reduction in both scattering efficiency[9,11] and signalto-noise in the measured scattering patterns.[12,13,14]. Recent experiments demonstrated that the FIC can be used to directly determine the structure of trapped ion pairs.[25,26] We point out that an alternative fluorescence imaging approach has been proposed by Ma and co-workers to measure the molecular structure from the interference of the emitted fluorescence from x-ray excited molecules with identical atoms.[27,28] Unlike FIC, this approach is related to measuring the first-order field correlation functions

Objectives

Results

Conclusion