Known for their stable structural and thermal properties, diamondoids and their radical cations are viable candidates as carriers for diffuse interstellar bands. 1 While previous diamondoid research has mainly focused on neutral molecules and their derivatives, little is known about their radical cations, which may form in interstellar environments by ionizing radiation. 2 We report the first experimental optical spectrum of the simplest diamondoid cation, the adamantane radical cation (C 10 H 16 + ), obtained via electronic photodissociation spectroscopy at 5 K between 310-1000 nm. The optical spectrum reveals a broad peak between 420-850 nm, assigned to the D 2 ( 2 E) ← D 0 ( 2 A 1 ) transition. This feature exhibits no vibrational structure, despite an experimental temperature below 20 K, due to lifetime broadening and/or Franck-Condon congestion. A second band system originating at 345 nm does reveal a vibrational progression and is attributed to the overlapping D 5 ( 2 A 1 )/D 6 ( 2 E) ← D 0 ( 2 A 1 ) transitions split by the Jahn-Teller effect. Comparison of the spectrum with known diffuse interstellar bands suggests that C 10 H 16 + is not likely to be a carrier. However, the strong absorption features in the UV to near IR show promise in the investigation of higher order diamondoid cations as potential candidates. 3

No abstract

Up to now, the response of antibiotics upon ionizing radiation has been very scarcely reported. Here, we present the results of X-ray photoabsorption experiments on isolated rifamycin, a broad-range antibiotic against Gram-positive and Gram-negative bacteria. A mass spectrometer has been coupled to a synchrotron beamline to analyze cationic products of photoabsorption on protonated rifamycin dimer and monomer sodium salts. Absorption of a single photon in the 100-300eV energy range leads to ionization of the molecular system, followed by vibrational energy deposition and subsequent inter-and/or intramolecular fragmentation. Interestingly, we observe a proton transfer from sodiated rifamycin to rifamycin, a widely observed process in ionized molecular systems in the gas phase. Moreover, we show that another charge-transfer process occurs in both dimer and monomer: intramolecular sodium transfer, which has not been reported yet, to the best of our knowledge.