Time-resolved photoelectron spectroscopy of proton transfer in the ground state of chloromalonaldehyde: Wave-packet dynamics on effective potential surfaces of reduced dimensionality

We report on a simple but widely useful method for obtaining time-independent potential surfaces of reduced dimensionality wherein the coupling between reaction and substrate modes is embedded by averaging over an ensemble of classical trajectories. While these classically averaged potentials with their reduced dimensionality should be useful whenever a separation between reaction and substrate modes is meaningful, their use brings about significant simplification in studies of time-resolved photoelectron spectra in polyatomic systems where full-dimensional studies of skeletal and photoelectron dynamics can be prohibitive. Here we report on the use of these effective potentials in the studies of dump-probe photoelectron spectra of intramolecular proton transfer in chloromalonaldehyde. In these applications the effective potentials should provide a more realistic description of proton-substrate couplings than the sudden or adiabatic approximations commonly employed in studies of proton transfer. The resulting time-dependent photoelectron signals, obtained here assuming a constant value of the photoelectron matrix element for ionization of the wave packet, are seen to track the proton transfer

Real-time observation of intramolecular proton transfer in the electronic ground state of chloromalonaldehyde: An ab initio study of time-resolved photoelectron spectra

The authors report on studies of time-resolved photoelectron spectra of intramolecular proton transfer in the ground state of chloromalonaldehyde, employing ab initio photoionization matrix elements and effective potential surfaces of reduced dimensionality, wherein the couplings of proton motion to the other molecular vibrational modes are embedded by averaging over classical trajectories. In the simulations, population is transferred from the vibrational ground state to vibrationally hot wave packets by pumping to an excited electronic state and dumping with a time-delayed pulse. These pump-dump-probe simulations demonstrate that the time-resolved photoelectron spectra track proton transfer in the electronic ground state well and, furthermore, that the geometry dependence of the matrix elements enhances the tracking compared with signals obtained with the Condon approximation. Photoelectron kinetic energy distributions arising from wave packets localized in different basins are also distinguishable and could be understood, as expected, on the basis of the strength of the optical couplings in different regions of the ground state potential surface and the Franck-Condon overlaps of the ground state wave packets with the vibrational eigenstates of the ion potential surface

Severity and Progression Rate of Cerebellar Ataxia in 16q-linked Autosomal Dominant Cerebellar Ataxia (16q-ADCA) in the Endemic Nagano Area of Japan

16q22.1-linked autosomal dominant cerebellar ataxia (16q-ADCA) is a recently defined subtype of ADCA identified by a disease-specific C/T substitution in the 5' untranslated region of the puratrophin-1 gene. In Nagano, the central mountainous district of the main island of Japan, 16q-ADCA and spinocerebellar ataxia type 6 (SCA6) are the most and second most prevalent subtypes of ADCA, respectively. Both subtypes are classified into Harding's ADCA III, but little attention has been given to the differences in the severity and progression rate of cerebellar ataxia between 16q-ADCA and SCA6. We investigated the clinical severity and progression rate of cerebellar ataxia of 16q-ADCA patients using international cooperative ataxia rating scale and scale for the assessment and rating of ataxia and compared them with those of SCA6 patients. The age at onset was much higher in 16q-ADCA patients (60.1 +/- 9.8 years, n = 66) than in SCA6 patients (41.1 +/- 8.7 years, n = 35). Clinical features of 16q-ADCA were basically consistent with pure cerebellar ataxia, as well as in SCA6, but gaze-evoked nystagmus was observed less frequently in 16q-ADCA patients than in SCA6 patients. When compared at almost the same disease duration after onset, the severity of cerebellar ataxia was a little higher, and the progression rate seemed more rapid in 16q-ADCA patients than in SCA6 patients, but the differences were not significant.ArticleCEREBELLUM. 8(1):46-51 (2009)journal articl

Late-onset spastic ataxia phenotype in a patient with a homozygous DDHD2 mutation

Autosomal recessive cerebellar ataxias and autosomal recessive hereditary spastic paraplegias (ARHSPs) are clinically and genetically heterogeneous neurological disorders. Herein we describe Japanese siblings with a midlife-onset, slowly progressive type of cerebellar ataxia and spastic paraplegia, without intellectual disability. Using whole exome sequencing, we identified a homozygous missense mutation in DDHD2, whose mutations were recently identified as the cause of early-onset ARHSP with intellectual disability. Brain MRI of the patient showed a thin corpus callosum. Cerebral proton magnetic resonance spectroscopy revealed an abnormal lipid peak in the basal ganglia, which has been reported as the hallmark of DDHD2-related ARHSP (SPG 54). The mutation caused a marked reduction of phospholipase A(1) activity, supporting that this mutation is the cause of SPG54. Our cases indicate that the possibility of SPG54 should also be considered when patients show a combination of adult-onset spastic ataxia and a thin corpus callosum. Magnetic resonance spectroscopy may be helpful in the differential diagnosis of patients with spastic ataxia phenotype.ArticleSCIENTIFIC REPORTS. 4:7132 (2014)journal articl

Nature of semiclassical spectrum in terms of classical trajectories(4) Quantum chaos and semiclassical theory in molecular science and nuclear theory, Chaos and Nonlinear Dynamics in Quantum-Mechanical and Macroscopic Systems)

この論文は国立情報学研究所の電子図書館事業により電子化されました。半古典量子化のメカニズムを詳細に検討し、半古典スペクトルの構成には、量子化される軌道だけでなく、量子化されるスペクトルの倍音等の間違ったスペクトルを消す軌道が重要な役割を果たすことを明らかにした。こうした研究に基づき、効率的に半古典スペクトルを計算する方法を提案し、2次元カオス系に適応した。さらに、この方法の利点を生かして固有状態に対応する古典軌道を抜き出し、その性質について議論した。The mechanism of semiclassical quantization is examined in detail. We found an important role of destructive interference in building quantum spectrum. Based on this analysis, we propose an efficient method to calculate the semiclassical spectrum. This method is particularly promising in multidimensional chaotic systems and also very useful to identify which trajectories dominate a quantum spectrum. We numerically examine this method by applying to a two-dimensional chaotic system and show an illustrative example of identifying such a dominant trajectory that corresponds to an eigenstate

Atomic-Scale Analysis of the RuO₂/Water Interface under Electrochemical Conditions

The structure of the interface between ruthenium oxide and water was examined using density functional theory calculations for a range of pH and electrode potential values, and the results were summarized in a surface Pourbaix diagram. The results indicate that pH affects the interfacial structure as a consequence of the formation of a stable hydrogen network and the impact of the electric field on the interfacial Gibbs energy. Focusing on the potential region of the oxygen evolution reaction (1.23 V vs a reversible hydrogen electrode (RHE) + overpotential), variations in pH were found to change both the formal Ru valency and the structure of the primary water layer by altering the work function of the interfacial structure. We hypothesize that the effects of pH on the hydrogen bond network and formal valency observed in this work also apply to other transition-metal oxides