Dissociation dynamics of the diamondoid adamantane upon photoionization by XUV femtosecond pulses

Sylvain Maclot,Jan Lahl,Fabian Brunner,Hélène Coudert-Alteirac,Sergio Díaz-Tendero,Piotr Rudawski,Per Johnsson,Suvasthika Indrajith,Patrick Rousseau,Bernd A Huber,Jasper Peschel,Néstor F Aguirre,Hampus Wikmark

doi:10.1038/s41598-020-59649-1

Abstract

This work presents a photodissociation study of the diamondoid adamantane using extreme ultraviolet femtosecond pulses. The fragmentation dynamics of the dication is unraveled by the use of advanced ion and electron spectroscopy giving access to the dissociation channels as well as their energetics. To get insight into the fragmentation dynamics, we use a theoretical approach combining potential energy surface determination, statistical fragmentation methods and molecular dynamics simulations. We demonstrate that the dissociation dynamics of adamantane dications takes place in a two-step process: barrierless cage opening followed by Coulomb repulsion-driven fragmentation.

Highlights

Diamondoids are a class of carbon nanomaterials based on carbon cages with well-defined structures formed by C(sp3)-C(sp3)-hybridized bonds and fully terminated by hydrogen atoms
When compared to laboratory measurements based on infrared spectroscopy[5], astronomical observations show a deficiency of diamondoids in the interstellar medium which to date is not completely understood[6]
The main fragments of the Cn groups n = 3, 4 and 8 are different from the ones found by Candian et al.[9], i.e. C3H7+, C4H+8 and C8H1+2 respectively, demonstrating that the dynamics of fragmentation is sensitive to the ionization/excitation energy

Summary

Introduction

Diamondoids are a class of carbon nanomaterials based on carbon cages with well-defined structures formed by C(sp3)-C(sp3)-hybridized bonds and fully terminated by hydrogen atoms. When compared to laboratory measurements based on infrared spectroscopy[5], astronomical observations show a deficiency of diamondoids in the interstellar medium which to date is not completely understood[6]. The first ionization limit in diamondoids lies around 8–9 eV with a maximum in the ionization yield between 10 and 11 eV7, close to the hydrogen Lyman-α line, and the efficient production of cations followed by dissociation has been suggested as a possible explanation for the apparent lack of diamondoids in the interstellar medium. In a recent work at the Swiss Light Source, vacuum ultraviolet radiation (9–12 eV) was used in combination with threshold photoelectron and photoion coincidence detection to determine the appearance energies and branching ratios of the resulting photofragments of the singly charged adamantane cation[9]. The support of various theoretical methods such as molecular dynamics simulations, potential energy surface determination and statistical fragmentation models, helps to unravel the fragmentation dynamics of such a complex molecular system

Methods

Results

Conclusion