Inner-Shell Photofragmentation of Adamantane: Probing ultrafast dynamics using synchrotron radiation

Adamantane (C₁₀H₁₆), the smallest diamondoid molecule has a symmetrical cage structure with two distinct types of carbon sites, namely CH and CH₂. When the molecule is core ionized or excited, it undergoes ultrafast structural reorganization and carbon cage opening. While theoretical models propose that the CH carbon site predominantly triggers this cage opening phenomenon, the specific role of the CH₂ site remains uncertain. In this work, we investigate the ultrafast dynamics of adamantane induced by soft X-ray irradiation using electron-ion coincidence spectroscopy. The fragmentation process of adamantane is complex and influenced by various competing relaxation pathways, including hydrogen loss, hydrogen migration, and the breaking of carbon-carbon bonds. Employing core ionization [1] and resonant excitation [2] with advanced theoretical calculations, we show that the fragmentation of adamantane's carbon cage is influenced by the specific carbon sites involved. Our findings reveal that certain fragmentation pathways exhibit sensitivity to the initial core-hole location, suggesting that different excitations of carbon sites could result in distinct mechanisms of cage opening.

[1] Ganguly, Smita, et al. "Coincidence study of core-ionized adamantane: site-sensitivity within a carbon cage?." Physical Chemistry Chemical Physics 24.47 (2022): 28994-29003.

[2] Ganguly, Smita, et al. "Resonant inner-shell photofragmentation of adamantane (C10H16)." Molecules 28.14 (2023): 5510.