25 research outputs found
A Preinstalled Protic Cation as a Switch for Superprotonic Conduction in a MetalāOrganic Framework
Metalāorganic frameworks (MOFs), made from various metal nodes and organic linkers, provide diverse research platforms for proton conduction. Here, we report on the superprotonic conduction of a Pt dimer based MOF, [Ptā(MPC)āClāCo(DMA)(HDMA)Ā·guest] (HāMPC, 6-mercaptopyridine-3-carboxylic acid; DMA, dimethylamine). In this framework, a protic dimethylammonium cation (HDMAāŗ) is trapped inside a pore through hydrogen bonding with an MPC ligand. Proton conductivity and X-ray measurements revealed that trapped HDMAāŗ works as a preinstalled switch, where HDMAāŗ changes its relative position and forms an effective proton-conducting pathway upon hydration, resulting in more than 105 times higher proton conductivity in comparison to that of the dehydrated form. Moreover, the anisotropy of single-crystal proton conductivity reveals the proton-conducting direction within the crystal. The present results offer insights into functional materials having a strong coupling of molecular dynamic motion and transport properties
Shock Excitation in Narrow Line Regions Powered by AGN Outflows
Outflows in the Active Galactic Nucleus (AGN) are considered to play a key
role in the host galaxy evolution through transfer of a large amount of energy.
A Narrow Line Region (NLR) in the AGN is composed of ionized gas extending from
pc-scales to kpc-scales. It has been suggested that shocks are required for
ionization of the NLR gas. If AGN outflows generate such shocks, they will
sweep through the NLR and the outflow energy will be transferred into a
galaxy-scale region. In order to study contribution of the AGN outflow to the
NLR-scale shock, we measure the
[\ion{Fe}{2}]/[\ion{P}{2}] line ratio, which is a
good tracer of shocks, using near-infrared spectroscopic observations with
WINERED (Warm INfrared Echelle spectrograph to Realize Extreme Dispersion and
sensitivity) mounted on the New Technology Telescope. Among 13 Seyfert galaxies
we observed, the [\ion{Fe}{2}] and [\ion{P}{2}] lines were detected in 12 and 6
targets, respectively. The [\ion{Fe}{2}]/[\ion{P}{2}] ratios in 4 targets were
found to be higher than 10, which implies the existence of shocks. We also
found that the shock is likely to exist where an ionized outflow, i.e., a blue
wing in [\ion{S}{3}], is present. Our result implies that the
ionized outflow present over a NLR-scale region sweeps through the interstellar
medium and generates a shock.Comment: Accepted for ApJ, 20 pages, 11 figure
Possible Progression of Mass-flow Processes around Young Intermediate-mass Stars Based on High-resolution Near-infrared Spectroscopy. I. Taurus
We used the WINERED spectrograph to perform near-infrared high-resolution spectroscopy (resolving power R = 28,000) of 13 young intermediate-mass stars in the Taurus star-forming region. Based on the presence of near- and mid-infrared continuum emission, young intermediate-mass stars can be classified into three different evolutionary stages: Phases I, II, and III in the order of evolution. Our obtained spectra (Ī» = 0.91ā1.35 Ī¼m) depict He i Ī»10830 and PĪ² lines that are sensitive to magnetospheric accretion and winds. We also investigate five sources each for PĪ² and He i lines that were obtained from previous studies along with our targets. We observe that the PĪ² profile morphologies in Phases I and II corresponded to an extensive variety of emission features; however, these features are not detected in Phase III. We also observe that the He i profile morphologies are mostly broad subcontinuum absorption lines in Phase I, narrow subcontinuum absorption lines in Phase II, and centered subcontinuum absorption features in Phase III. Our results indicate that the profile morphologies exhibit a progression of the dominant mass-flow processes: stellar wind and probably magnetospheric accretion in the very early stage, magnetospheric accretion and disk wind in the subsequent stage, and no activities in the final stage. These interpretations further suggest that opacity in protoplanetary disks plays an important role in mass-flow processes. Results also indicate that He i absorption features in Phase III sources, associated with chromospheric activities even in such young phases, are characteristics of intermediate-mass stars