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We have investigated multiphoton multiple ionization dynamics of argon and xenon atoms using a new x-ray free electron laser (XFEL) facility, SPring-8Ångstrom Compact free electron LAser (SACLA) in Japan, and identified that Xe n+ with n up to 26 are produced predominantly via four-photon absorption as well as Ar n+ with n up to 10 are produced via two-photon absorption at a photon energy of 5.5 keV. The absolute fluence of the XFEL pulse, needed for comparison between theory and experiment, has been determined using two-photon processes in the argon atom with the help of benchmark ab initio calculations. Our experimental results, in combination with a newly developed theoretical model for heavy atoms, demonstrate the occurrence of multiphoton absorption involving deep inner shells.

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Male-specific exaggerated horns are an evolutionary novelty and have diverged rapidly via intrasexual selection. Here, we investigated the function of the conserved sex-determination gene doublesex (dsx) in the Japanese rhinoceros beetle (Trypoxylus dichotomus) using RNA interference (RNAi). Our results show that the sex-specific T. dichotomus dsx isoforms have an antagonistic function for head horn formation and only the male isoform has a role for thoracic horn formation. These results indicate that the novel sex-specific regulation of dsx during horn morphogenesis might have been the key evolutionary developmental event at the transition from sexually monomorphic to sexually dimorphic horns.

Future tonne-scale liquefied noble gas detectors depend on efficient light detection in the VUV range. In the past years Silicon Photomultipliers (SiPMs) have emerged as a valid alternative to standard photomultiplier tubes or large area avalanche photodiodes. The next generation double beta decay experiment, nEXO, with a 5 tonne liquid xenon time projection chamber, will use SiPMs for detecting the 175 nm xenon scintillation light, in order to achieve an energy resolution of σ/Qββ = 1 %. This paper presents recent measurements of the VUV-HD generation SiPMs from Fondazione Bruno Kessler in two complementary setups. It includes measurements of the photon detection efficiency with gaseous xenon scintillation light in a vacuum setup and dark measurements in a dry nitrogen gas setup. We report improved photon detection efficiency at 175 nm compared to previous generation devices, that would meet the criteria of nEXO. Furthermore, we present the projected nEXO detector light collection and energy resolution that could be achieved by using these SiPMs. Index Terms-silicon photomultiplier, xenon detectors, photo detectors, vacuum ultra-violet light, nEXO I. NEUTRINO-LESS DOUBLE BETA DECAY AND NEXO N eutrino-less double beta decay (0νββ) is a hypothetical nuclear decay where two neutrons decay into two protons and two electrons are emitted but no anti-neutrinos are present in the final state. The observation of this process would have a fundamental impact on the Standard Model of Particle Physics, specifically showing a violation of lepton number conservation (|∆L| = 2), and would imply that the neutrino is a Majorana fermion [1], independently of the actual process enabling the decay [2]. Furthermore, the half-life of the decay would shed light on the absolute neutrino mass scale [3]. The nEXO collaboration plans to build a cylindrical singlephase time projection chamber (TPC) filled with 5 tonnes of liquid xenon (LXe), with 90 % enrichment in 136 Xe [4]. nEXO takes advantage of the experience from its predecessor EXO-200 [5], but will incorporate new light and charge detectors [6]. Together with cold electronics sitting inside the LXe, this allows nEXO to achieve an energy resolution of σ/Q ββ = 1 % for the 0νββ decay of 136 Xe (2458.07 ± 0.31 keV [7], [8]).In particular, instead of the EXO-200 Large Area Avalanche Photo-diodes (LAAPDs), nEXO will use Silicon Photomultipliers (SiPMs) for the detection of xenon scintillation light. The SiPMs will fully cover the lateral surface of the cylinder with a total photo-sensitive area of about 4 m 2 , as shown in Figure 1. The devices will be immersed in LXe and placed in the high field region behind the field shaping rings of the TPC field cage [9]. The performance of SiPMs has improved significantly over the past decade and they are especially interesting because of their high gain, on the order of 10 6 , and their single photon resolution capability.The half-life sensitivity of nEXO to the 0νββ decay of 136 Xe is projected to be 9.5 × 10 27 yr for 90 % C.L. after 10 years o...

In recent years, free-electron lasers operating in the true X-ray regime have opened up access to the femtosecond-scale dynamics induced by deep inner-shell ionization. We have investigated charge creation and transfer dynamics in the context of molecular Coulomb explosion of a single molecule, exposed to sequential deep inner-shell ionization within an ultrashort (10 fs) X-ray pulse. The target molecule was CH3I, methane sensitized to X-rays by halogenization with a heavy element, iodine. Time-of-flight ion spectroscopy and coincident ion analysis was employed to investigate, via the properties of the atomic fragments, single-molecule charge states of up to +22. Experimental findings have been compared with a parametric model of simultaneous Coulomb explosion and charge transfer in the molecule. The study demonstrates that including realistic charge dynamics is imperative when molecular Coulomb explosion experiments using short-pulse facilities are performed.

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Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at ~5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo- and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays.