Gas-phase singly protonated organic molecules of mass 410 Da (Alexa Fluor 350) have been cooled from ambient temperature to the hundred millikelvin range by Coulomb interaction with laser-cooled barium ions. The molecules were generated by an electrospray ionization source, transferred to and stored in a radio-frequency trap together with the atomic ions. Observations are well described by molecular dynamics simulations, which are used to determine the spatial distribution and thermal energy of the molecules. In one example, an ensemble of 830 laser-cooled ${}^{138}\mathrm{Ba}^{+}$ ions cooled 200 molecular ions to less than 115 mK. The demonstrated technique should allow a large variety of protonated molecules to be sympathetically cooled, including molecules of much higher mass, such as proteins.

Theoretical calculations predict ${}^{270}\mathrm{Hs}$ ($Z=108$, $N=162$) to be a doubly magic deformed nucleus, decaying mainly by $\alpha$-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the ${}^{26}\mathrm{Mg}+{}^{248}\mathrm{Cm}$ reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide ${}^{270}\mathrm{Hs}$, which decays by $\alpha$-particle emission with $Q_{\alpha }=9.02\pm 0.03\mathrm{MeV}$ to ${}^{266}\mathrm{Sg}$ which undergoes spontaneous fission with a half-life of ${444}_{-148}^{+444}\mathrm{ms}$. A production cross section of about 3 pb was measured for ${}^{270}\mathrm{Hs}$. Thus, ${}^{270}\mathrm{Hs}$ is the first nucleus for which experimental nuclear decay properties have become available for comparison with theoretical predictions of the $N=162$ shell stability.

We report the statistical analysis of the movement of a submicron particle confined in a harmonic potential in the presence of a torque. The absolute value of the torque can be found from the auto- and cross-correlation functions of the particle’s coordinates. We experimentally prove this analysis by detecting the torque produced onto an optically trapped particle by an optical beam with orbital angular momentum.

Horseshoe bats emit their ultrasonic biosonar pulses through nostrils surrounded by intricately shaped protuberances (noseleaves). While these noseleaves have been hypothesized to affect the sonar beam, their physical function has never been analyzed. Using numerical methods, we show that conspicuous furrows in the noseleaf act as resonance cavities shaping the sonar beam. This demonstrates that (a) animals can use resonances in external, half-open cavities to direct sound emissions, (b) structural detail in the faces of bats can have acoustic effects even if it is not adjacent to the emission sites, and (c) specializations in the biosonar system of horseshoe bats allow for differential processing of subbands of the pulse in the acoustic domain.

Twining plants achieve vertical growth by revolving around supports of different sizes on which they exert a pressure. This observation raises many intriguing questions that are addressed within the framework of elastic filamentary structures by modeling the stem close to the apex as a growing elastic rod. The analysis shows that vertical growth is achieved thanks to discrete contact points and regions with continuous contact, that the contact pressure creates tension in the stem as observed experimentally, and that there is a maximal radius of the pole around which a twiner can climb.

A light beam changes direction as it enters a liquid at an angle from another medium, such as air. Should the liquid contain molecules that lack mirror symmetry, then it has been predicted by Fresnel that the light beam will not only change direction, but will actually split into two separate beams with a small difference in the respective angles of refraction. Here we report the observation of this phenomenon. We also demonstrate that the angle of reflection does not equal the angle of incidence in a chiral medium. Unlike conventional optical rotation, which depends on the path-length through the sample, the reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.

We discuss the issue of quasiparticle production by “analogue black holes” with particular attention paid to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that, in order to obtain a stationary and Planckian emission of quasiparticles, it is not necessary to create a trapped region in the acoustic spacetime (corresponding to a supersonic regime in the fluid flow). It is sufficient to set up a dynamically changing flow asymptotically approaching a sonic regime with sufficient rapidity in laboratory time. This result is generic to curved-space quantum field theory, the “analogue spacetimes” we consider providing a guide to physical intuition, and a possible route to laboratory experiments.

We observe the movement of water over time between pores of differing sizes in Castlegate sandstone. To achieve this, we perform an NMR transverse relaxation exchange experiment for several mixing times. The resulting data are converted to 2D $T_2$ distributions using a 2D inverse Laplace transform (ILT). We show for the first time that quantitative analysis of ILT distributions enables one to extract characteristic times for different pores sizes. This information is potentially useful for permeability determination as well as better understanding of exchange between specific pore subpopulations.

We demonstrate up-conversion of noncoherent sunlight realized by ultralow excitation intensity. The bimolecular up-conversion process in our systems relies on the presence of a metastable triplet excited state, and thus has dramatically different photophysical characteristics relative to the other known methods for photon up-conversion (two-photon absorption, parametric processes, second harmonic generation, sequential multiphoton absorption, etc.).

We report the first observation of the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 eV and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum. The magnitude of these sidebands as a function of time delay between the laser and extreme ultraviolet pulses represents a cross-correlation measurement of the extreme ultraviolet pulse. This effect promises to be useful to extend extreme ultraviolet pulse duration measurements to higher photon energies, as well as opening up femtosecond-to-attosecond time-scale electron dynamics in solid and surface-adsorbate systems.

In response to an external, microwave-frequency magnetic field, a paramagnetic medium will absorb energy from the field that drives the magnetization dynamics. Here we describe a new process by which an external spin-injection source, when combined with the microwave field spin pumping, can drive the paramagnetic medium from one that absorbs microwave energy to one that emits microwave energy. We derive a simple condition for the crossover from absorptive to emissive behavior. Based on this process, we propose a solid-state, paramagnetic device in which microwave amplification by stimulated emission of radiation is driven by spin injection.

We consider the modulational instability of nonlinearly interacting two-dimensional waves in deep water, which are described by a pair of two-dimensional coupled nonlinear Schrödinger equations. We derive a nonlinear dispersion relation. The latter is numerically analyzed to obtain the regions and the associated growth rates of the modulational instability. Furthermore, we follow the long term evolution of the latter by means of computer simulations of the governing nonlinear equations and demonstrate the formation of localized coherent wave envelopes. Our results should be useful for understanding the formation and nonlinear propagation characteristics of large-amplitude freak waves in deep water.

When an atom absorbs a photon from a laser beam that is not an infinite plane wave, the atom’s recoil is less than $\hslash k$ in the propagation direction. We show that the recoils in the transverse directions produce a lensing of the atomic wave functions, which leads to a frequency shift that is not discrete but varies linearly with the field amplitude and strongly depends on the atomic state detection. The same lensing effect is also important for microwave atomic clocks. The frequency shifts are of the order of the naive recoil shift for the transverse wave vector of the photons.

The classical “brick wall,” which may, according to quantum mechanics, leak via tunneling, is here shown to be completely transparent when appropriate impedance matching media are placed both in front of and behind the “wall.” Optical experiments involving beyond-critical-angle-tunnel barriers in the frustrated total internal reflection scheme which mimic quantum mechanical systems provide convincing proof of this remarkable effect. The same mechanism also allows vastly enhanced transmission through unstructured thin metal films without the need for surface wave excitation.

We conduct an experimental investigation of nonlinearity management in optics using femtosecond pulses and layered Kerr media consisting of glass and air. By examining the propagation properties over several diffraction lengths, we show that wave collapse can be prevented. We corroborate these experimental results with numerical simulations of the ($2+1$)-dimensional focusing cubic nonlinear Schrödinger equation with piecewise constant coefficients and a theoretical analysis of this setting using a moment method.

A Rydberg atom mirror has been designed and its operational principle tested experimentally. A supersonic expansion containing H atoms moving with a velocity of $720\mathrm{m}/\mathrm{s}$ initially propagates toward a quadrupolar electrostatic mirror. The H atoms are then photoexcited to $n=27\mathrm{Rydberg}$ states with a positive Stark shift and move in a rapidly increasing electric field. The H atom beam is stopped in $4.8\mu \mathrm{s}$, only 1.9 mm away from the photoexcitation spot, and is then reflected back. The reflection process is monitored by pulsed field ionization and imaging.

We report the first observation of anti-Stokes laser-induced cooling in the ${\mathrm{Er}}^{3+}:{\mathrm{KPb}}_2{\mathrm{Cl}}_5$ crystal and in the ${\mathrm{Er}}^{3+}:\mathrm{CNBZn}$ (${\mathrm{CdF}}_2\mathrm{\text{−}}{\mathrm{CdCl}}_2\mathrm{\text{−}}\mathrm{NaF}\mathrm{\text{−}}{\mathrm{BaF}}_2\mathrm{\text{−}}{\mathrm{BaCl}}_2\mathrm{\text{−}}{\mathrm{ZnF}}_2$) glass. The internal cooling efficiencies have been calculated by using photothermal deflection spectroscopy. Thermal scans acquired with an infrared thermal camera proved the bulk cooling capability of the studied samples. The implications of these results are discussed.

An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus ${}^{11}\mathrm{Li}$ at $70\mathrm{MeV}/\mathrm{nucleon}$ at RIKEN. Strong low-energy (soft) $E1$ excitation is observed, peaked at about $E_{\mathrm{x}}=0.6\mathrm{MeV}$ with $B(E1)=1.42(18){\mathrm{e}}^2{\mathrm{fm}}^2$ for $E_{\mathrm{rel}}\le 3\mathrm{MeV}$, which was largely missed in previous measurements. This excitation represents the strongest $E1$ transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the $E1$ non-energy-weighted cluster sum rule.

We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle level are the same as those found in simulations of equilibrium hard disks. This direct mapping suggests that the study of equilibrium systems can be effectively applied to study nonequilibrium steady states such as those found in our driven and dissipative granular system.

Computer simulations show that end-grafted immiscible homopolymers can confer multivalence to nanoparticles, resulting in soft nanopolyhedra with structures identical to those found in small clusters of colloidal microspheres. Unprecedented structure tunability is demonstrated by several structure transition sequences, including a reentrant transition, induced by varying composition, polymer lengths, or grafting patterns. These results suggest a new method for fabricating nanoparticles with precisely controlled numbers and locations of functional sites (i.e., multivalent nanoparticles).