Three-dimensional (3D) velocity map imaging: from technique to application

The velocity map imaging (VMI) technique was first introduced by Eppink and Parker in 1997, as an improvement to the original ion imaging method by Houston and Chandler in 1987. The method has gained huge popularity over the past two decades and has become a standard tool for measuring high-resolution translational energy and angular distributions of ions and electrons. VMI has evolved gradually from 2D momentum measurements to 3D measurements with various implementations and configurations. The most recent advancement has brought unprecedented 3D performance to the technique in terms of resolutions (both spatial and temporal), multi-hit capability as well as acquisition speed while maintaining many attractive attributes afforded by conventional VMI such as being simple, cost-effective, visually appealing and versatile. In this tutorial we will discuss many technical aspects of the recent advancement and its application in probing correlated chemical dynamics.

The Relativistic and the Hidden Momentum of Minkowski and Abraham in Relativistic Energy Wave

An analysis of the consistency of the Abraham and Minkowski momenta in the determination of the photon trajectory was carried out considering a new principle of conservation of the photon's mechanical energy, in which the photon conserves translational energy in orbital angular momentum when transiting between two media, introducing the relativistic energy wave (REW). The confrontation between REW and the recent theory of space-time waves (ST) was considered, pondering your differences. Throughout this study it was possible to verify that the Abraham momentum appears a relativistic photon ignition device in the transition between two media, acting as the hidden momentum of the Minkowski’s relativistic momentum. The wavy behavior in the matter is relativistic, and the relativistic trajectory appears with delays and advances, with points of synchronization between source-observer. The classical or relativistic trajectories are determined as a function of the angle of incidence and the relative refractive index, by one of two distinct non-additive torques, the classic by Abraham or the relativistic by Minkowski. It was found that the same analysis conducted under the principle of conservation of the mechanical energy of the photon can be treated by an new Doppler, Relativistic Apparent, that can be confused with other Dopplers in the treatment of redshift from distant sources. It was found that the conservation of energy in Orbital Angular Momentum (OAM), in the interaction with matter, explains that the synchronization instants are found in the inversion of the OAM, where the advances and delays of REW occur under negligible variations of the OAM, however, opposites.

Terahertz Driven Ultrafast Energy Dissipation in Aqueous Ionic Solutions

Solvation of ions changes the physical, chemical and thermodynamic properties of water. The microscopic origin of this process is believed to be the ion-induced perturbation in the structure and dynamics of the hydrogen (H)-bonding network of water. Here, we provide microscopic insight on the local structural deformation of the H-bonding network of water by ions, via investigating the dissipation of external energy in salt solutions by a novel time-resolved terahertz (THz)-Raman spectroscopy. We resonantly drive the low-frequency rotational dynamics of water molecules by intense THz pulses and probe the Raman response of their intermolecular translational motions. We find that the intermolecular rotational-to-translational energy transfer is enhanced by highly-charged cations and it is drastically reduced by highly-charged anions, scaling with the ion surface charge density and concentration. Our molecular dynamics simulations further reveal that the water-water H-bond strength between the first and the second solvation shells of cations (anions) increases (decreases), signifying the opposite effects of cations and anions on the local structure of water. The impact of ion polarity on the ultrafast energy dissipation in water, resembles the effect of ions on stabilization and denaturation of proteins.

Wobbling double sine-Gordon kinks

We study the collision of a kink and an antikink in the double sine-Gordon model with and without the excited vibrational mode. In the latter case, we find that there is a limited range of the parameters where the resonance windows exist, despite the existence of a vibrational mode. Still, when the vibrational mode is initially excited, its energy can turn into translational energy after the collision. This creates one-bounce as well as a rich structure of higher-bounce resonance windows that depend on the wobbling phase being in or out of phase at the collision and the wobbling amplitude being sufficiently large. When the vibrational mode is excited, the modified structure of one-bounce windows is observed in the whole range of the model’s parameters, and the resonant interval with higher-bounce windows gradually increases with the wobbling amplitude. We estimated the center of the one-bounce windows using a simple analytical approximation for the wobbling evolution. The kinks’ final wobbling frequency is Lorentz contracted, which is simply derived from our equations. We also report that the maximum energy density value always has a smooth behavior in the resonance windows.

The climate roles of H2O and CO2 from longwave absorption

In search for reproducibility of the results from sophisticated scientific research, the present work focuses on the longwave absorption in the atmosphere. It is found that the variability of Earth’s surface temperature follows a near-proportional relationship between the atmospheric trace gas concentrations of water vapor and CO2, and longwave absorption. Furthermore, estimates are attempted on the CO2 V/R-T (vibrational/rotational-to-translational) energy transfer as a dominant heating process.

Photodissociation Dynamics of the Cyclohexyl Radical from the 3p Rydberg State at 248 nm

The photodissociation of jet-cooled cyclohexyl was studied by exciting the radicals to their 3p Rydberg state using 248 nm laser light and detecting photoproducts by photofragment translational spectroscopy. Both H-atom loss and dissociation to heavy fragment pairs are observed. The H-atom loss channel exhibits a two-component translational energy distribution. The fast photoproduct component is attributed to impulsive cleavage directly from an excited state, likely the Rydberg 3s state, forming cyclohexene. The slow component is due to statistical decomposition of hot cyclohexyl radicals that internally convert to the ground electronic state prior to H-atom loss. The fast and slow components are present in a ~0.7:1 ratio, similar to findings in other alkyl radicals. Internal conversion to the ground state also leads to ring-opening followed by dissociation to 1-buten-4-yl + ethene in comparable yield to H-loss, with the C₄H₇ fragment containing enough internal energy to dissociate further to butadiene via H-atom loss. A very minor ground-state C₅H₈ + CH₃ channel is observed, attributed predominantly to 1,3-pentadiene formation. The ground-state branching ratios agree well with RRKM calculations, which also predict C₄H₆ + C₂H₅ and C₃H₆ + C₃H₅ channels with similar yield to C₅H₈ + CH₃. If these channels were active it was at levels too low to be observed.

Photodissociation Dynamics of the Cyclohexyl Radical from the 3p Rydberg State at 248 nm

The photodissociation of jet-cooled cyclohexyl was studied by exciting the radicals to their 3p Rydberg state using 248 nm laser light and detecting photoproducts by photofragment translational spectroscopy. Both H-atom loss and dissociation to heavy fragment pairs are observed. The H-atom loss channel exhibits a two-component translational energy distribution. The fast photoproduct component is attributed to impulsive cleavage directly from an excited state, likely the Rydberg 3s state, forming cyclohexene. The slow component is due to statistical decomposition of hot cyclohexyl radicals that internally convert to the ground electronic state prior to H-atom loss. The fast and slow components are present in a ~0.7:1 ratio, similar to findings in other alkyl radicals. Internal conversion to the ground state also leads to ring-opening followed by dissociation to 1-buten-4-yl + ethene in comparable yield to H-loss, with the C₄H₇ fragment containing enough internal energy to dissociate further to butadiene via H-atom loss. A very minor ground-state C₅H₈ + CH₃ channel is observed, attributed predominantly to 1,3-pentadiene formation. The ground-state branching ratios agree well with RRKM calculations, which also predict C₄H₆ + C₂H₅ and C₃H₆ + C₃H₅ channels with similar yield to C₅H₈ + CH₃. If these channels were active it was at levels too low to be observed.

Reversible 1D chain-reaction gives rise to an atomic-scale Newton’s cradle

An F-atom with ~ 1 eV translational energy was aimed at a line of fluorocarbon adsorbates on Cu(110). Sequential ‘knock-on’ of F-atom products was observed by STM to propagate along...