From photoelectron detachment spectra of BrHBr−, BrDBr− and IHI−, IDI− to vibrational bonding of BrMuBr and IMuI

Photoelectron detachment XLX−(0000) + hν → XLX(vib) + e − + KER (X = Br or I, L = H or D) at sufficiently low temperatures photoionizes linear dihalogen anions XLX− in the vibrational ground state (v 1 v 2 l v 3 = 0000) and prepares the neutral radicals XLX(vib) in vibrational states (vib). At the same time, part of the photon energy (hν) is converted into kinetic energy release (KER) of the electron [R. B. Metz, S. E. Bradforth, and D. M. Neumark, Adv. Chem. Phys. 81, 1 (1992)]. The process may be described approximately in terms of a Franck-Condon type transfer of the vibrational wavefunction representing XLX−(0000) from the domain close to the minimum of its potential energy surface (PES) to the domain close to the linear transition state of the PES of the neutral XLX. As a consequence, prominent peaks of the photoelectron detachment spectra (pds) correlate with the vibrational energies E XLX,vib of states XLX(vib) which are centered at linear transition state. The corresponding vibrational quantum numbers may be labeled vib = (v 1 v 2 l v 3) = (000 v 3). Accordingly, the related most prominent peaks in the pds are labeled v 3. We construct a model PES which mimics the “true” PES in the domain of transition state such that it supports vibrational states with energies E XLX,pds,000v3 close to the peaks of the pds labeled v 3 = 0, 2, and 4. Subsequently, the same model PES is also used to calculate approximate values of the energies E XMuX,0000 of the isotopomers XMuX(0000). For the heavy isotopomers XHX and XDX, it turns out that all energies E XLX,000 v 3 are above the threshold for dissociation, which means that all heavy XLX(000 v 3) with wavefunctions centered at the transition state are unstable resonances with finite lifetimes. Turning the table, bound states of the heavy XLX are van der Waals (vdW) bonded. In contrast, the energies E XMuX,0000 of the light isotopomers XMuX(0000) are below the threshold for dissociation, with wavefunctions centered at the transition state. This means that XMuX(0000) are vibrationally bonded. This implies a fundamental change of the nature of chemical bonding, from vdW bonding of the heavy XHX, XDX to vibrational bonding of XMuX. For BrMuBr, the present results derived from experimental pds of BrHBr− and BrDBr− confirm the recent discovery of vibrational bonding based on quantum chemical ab initio calculations [D. G. Fleming, J. Manz, K. Sato, and T. Takayanagi, Angew. Chem., Int. Ed. 53, 13706 (2014)]. The extension from BrLBr to ILI means the discovery of a new example of vibrational bonding. These empirical results for the vibrational bonding of IMuI, derived from the photoelectron spectra of IHI− and IDI−, are supported by ab initio simulations of the spectra and of the wavefunction representing vibrational bonding of IMuI

FORWARD AND FALSE STEP TECHNIQUES USED FOR SPRINT START IN A SIDEWAYS DIRECTION: WHICH IS SUPERIOR?

The purpose of this study was to determine which technique is superior to in a standing sprint start in a sideways direction: the false step or forward step technique. Nine males performed 5 m sprints in a rightward direction starting with these two techniques. They took a first step in their right side with their right foot in the forward step trials, whereas they took a first step in their left side with their left foot in the false step trials. No significant differences were found between the two trial conditions in the sprint times for 1 m, 2 m, 3 m and 4 m. These results indicate that the start techniques made no difference in the performance in the sideways direction, although the superiority of the false step technique for the forward sprint start was reported previously. This finding suggests that the superiority of the sprint start techniques is dependent on the sprint direction

DETERMINATION OF THE OPTIMAL NUMBER OF RIGID-BODY SEGMENTS TO REPRESENT THE TRUNK USING AKAIKE’S INFORMATION CRITERION

The purpose of this study was to determine the optimal number of rigid body segments to sufficiently represent the trunk movements, using Akaike’s information criterion. The trunk in static and dynamic conditions was modelled with one, two, three, or six linked rigid-body representations. The difference in the three-dimensional position between the actual and modelled data was calculated to quantify how well these models describe the actual trunk kinematics. The Akaike’s information criterion was calculated using the difference in position data to evaluate the goodness-of-fit for each model. Our findings suggest that two-linked rigid-body representation may be good enough when analysing trunk movements except when the movement includes a large axial rotation, for which the three-linked rigid-bodies would be better. These results would be useful in determining the optimal number of rigid body representation to sufficiently represent the trunk movements

THE RELATIONSHIP BETWEEN TRUNK KINEMATIC VARIABLES AND UNDERWATER UNDULATORY SWIMMING PERFORMANCE IN COMPETITIVE SWIMMERS

The purpose of this study was to examine the relationship between selected trunk kinematic variables and undulatory underwater swimming performance in competitive swimmers. Eight male and 2 female swimmers performed 15 m UUS with their maximum efforts. Three-dimensional coordinate of markers attached to bony configurations were corrected during Pearson’s product moment by using the underwater motion capture system. The range of motion and the corresponding angular velocity were computed for lower waist, upper waist and chest. The relationship between horizontal velocity of center of mass and each kinematic variable was then examined. No significant correlations were found between horizontal velocity and each range of motion. The horizontal velocity was significantly correlate with the angular velocity of lower waist and of chest, but not with the corresponding value of upper waist. The current results suggest that the swimmers produce the great horizontal velocity by increase in trunk angular velocities rather than by increase in trunk range of motion