On nanotextured noble-metal surfaces, surface-enhanced Raman scattering (SERS) is observed, where enhanced by a factor, G, that frequently about one million, but underlying the factor G broad distribution of local enhancement factors, eta. We have measured this for benzenethiolate molecules on 330-nanometer silver-coated nanosphere lattice using incident light wavelength 532 nanometers. A series laser pulses with increasing electric fields burned away at sites progressively decreasing...

At the level of individual molecules, familiar concepts heat transport no longer apply. When large amounts are transported through a molecule, crucial process in molecular electronic devices, energy is carried by discrete vibrational excitations. We studied self-assembled monolayers long-chain hydrocarbon molecules anchored to gold substrate ultrafast heating with femtosecond laser pulse. reached methyl groups at chain ends, nonlinear coherent spectroscopy technique detected resulting...

Lowering the overpotential for electrochemical conversion of CO2 to useful products is one grand challenges in Department Of Energy report, "Catalysis Energy". In a previous paper, we showed that occurs at low on 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4)-coated silver catalyst an aqueous solution EMIM-BF4. One surprises paper was selectivity CO better than 96% silver, compared with ∼80% absence ionic liquid. this article, use sum frequency generation (SFG) explore mechanism...

A model and detailed calculations are presented to describe the flow of energy in a shocked solid consisting large organic molecules. The shock excites bulk phonons, which rapidly achieve state phonon equilibrium characterized by quasitemperature. excess subsequently flows into molecular vibrations, vibrational multiphonon up pumping process occurs because anharmonic coupling terms potential surface. Of central importance lowest or ‘‘doorway’’ modes, through mechanical enters leaves Using...

In the broad water stretching band (2900−3700 cm-1), frequency-dependent vibrational energy relaxation (VER), and spectral diffusion both occur on time scale of a few picoseconds. Ultrafast IR−Raman spectroscopy is used to study processes. VER also studied in solutions HDO D2O (HDO/D2O). The OH stretch (νOH) lifetime for ∼1 ps. OD (νOD) ∼2 Stretch decay generates substantial excitation bending modes. lifetimes vibrations (δ) H2O, HDO, can be estimated 0.6 ps ≤ T1 1.2 range. νOH produces δH2O...

Energy transport in molecular solids is investigated using a picosecond transient-grating technique. A model presented which directly relates the rate of energy to experimental observable. The diffusion coefficient for singlet electronic excitation reported pentacene $p$-terphenyl. Acoustically induced optical absorption effects are also observed.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemical reaction initiation and hot-spot formation in shocked energetic molecular materialsA. Tokmakoff, M. D. Fayer, Dana DlottCite this: J. Phys. Chem. 1993, 97, 9, 1901–1913Publication Date (Print):March 1, 1993Publication History Published online1 May 2002Published inissue 1 March 1993https://pubs.acs.org/doi/10.1021/j100111a031https://doi.org/10.1021/j100111a031research-articleACS PublicationsRequest reuse permissionsArticle...

Suppression of the nonresonant background in vibrational sum-frequency generation (SFG) broadband multiplex configuration is achieved using a time-asymmetric pulse, created by passing femtosecond pulse through Fabry−Perot étalon, to temporally discriminate between faster and slower resonant contributions. A mixed time frequency domain explanation SFG process presented, spectra with high resolutions degrees suppression are obtained self-assembled alkanethiolate monolayers on Au.

Ultrafast nonlinear vibrational spectroscopy with mid-IR pumping and incoherent anti-Stokes Raman probing is used to study v = 1 excitations of OH stretching (νOH) water HOD in D2O solvent (HOD/D2O). The parent νOH decay the appearance daughter bending are simultaneously monitored, which allows for characterization stretch pathways. At all times pump frequencies within band, excited-state spectrum can be fit by two overlapping subbands, a broader red-shifted band narrower blue-shifted . We...

We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). studied different designs launched by laser pulses energies, pulse durations beam diameters, that produced km s−1 impacts with transparent materials. Laser-launching flyers 25–100 μm thick cemented to glass substrates is usually thought involve vaporization a portion flyer, which creates many difficulties associated loss integrity heating material. However, in system used...

Mechanical action can produce dramatic physical and mechanochemical effects when the energy is spatially or temporally concentrated. An important example of such phenomena in solids mechanical initiation explosions, which has long been speculated to result from ‘hot spot’ generation at localized microstructures energetic material. Direct experimental evidence hot spots, however, exceptionally limited; mechanisms for their are poorly understood methods control locations remain elusive. Here...

Metal–organic frameworks (MOFs) have potential applications as energy absorbing materials for shock wave mitigation due to their nanoporosity. Here we examined km/s laser-driven flyer plate impacts on a prototypical MOF, ZIF-8. We observed particle fragmentation and morphological changes in microcrystals of ZIF-8 at lower pressures (≈2.5 GPa), amorphization structural collapse higher (≈8 GPa). High-speed emission spectroscopy revealed that 50 ns after impacts, an pulse was generated by...

Recent investigations into the mechanical properties and mechanochemical reactions of metal-organic frameworks (MOFs) have suggested potential for energy dissipation by multiple mechanisms. Although possibility efficient multifunctional shock MOFs was static high pressure studies, there is little known about under compression. Here, we measure attenuation wave MOF denoted zeolitic-imidazolate framework (ZIF-8) in its desolvated, porous state. We find that ZIF-8 occurred processes: powder...

In a suspension of reverse micelles, in which the surfactant sodium dioctyl sulfosuccinate (AOT) separates water nanodroplet from bulk nonpolar CCl4 phase, ultrafast vibrational spectroscopy was used to study energy transfer through AOT interfacial monolayer surrounding CCl4. Most transferred polar head group within 1.8 picoseconds and then out 10 picoseconds. Vibrational pumped directly into tail resulted slower 20- 40-picosecond

Ultrafast spectroscopy was used to study vibrational energy transfer between reporter groups on different parts of a molecule in liquid. When OH stretching vibrations alcohols were excited by mid-infrared laser pulses, observed move through intervening CH2 or CH groups, taking steps up and down energy, ending at terminal CH3 groups. For each additional group the path CH3, time for increased about 0.4 picosecond.

Vibrational energy relaxation (VER) of neat methanol at ambient temperature is studied with a three-dimensional vibrational spectroscopy technique. The first two dimensions are represented by time series incoherent anti-Stokes Raman spectra given mid-IR pump frequency. third dimension involves changing the frequency within manifold CH and OH stretching transitions ν(CH) ν(OH). Each 2D representation shows VER dynamics occurring as result pumping specific transition. decay pumped transition...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLigand binding to heme proteins: relevance of low-temperature dataAnjum Ansari, Ernesto E. Di Iorio, Dana D. Dlott, Hans Frauenfelder, Icko T. Iben, Peter Langer, Heinrich Roder, Todd B. Sauke, and Erramilli ShyamsunderCite this: Biochemistry 1986, 25, 11, 3139–3146Publication Date (Print):June 3, 1986Publication History Published online1 May 2002Published inissue 3 June 1986https://doi.org/10.1021/bi00359a011RIGHTS & PERMISSIONSArticle...

Ultrafast anti-Stokes Raman scattering after intense mid-IR excitation is used to study vibrational energy relaxation (VER) and cooling (VC) in neat liquid acetonitrile. The pulse (3000 cm-1) excites a combination of C−H stretching fundamentals bending overtones, which are coupled by Fermi resonance. Vibrational decays from the pumped stretch 5 ps. Almost no transferred C⋮N (2253 cm-1). behaves as VER “blocking group” keeps CH3−C moiety. A ps buildup, mirrors decay, seen modes (∼1500 at...

A significant recent development in the field of energetic materials has been introduction nanotechnology. Nanoparticle based have potential releasing more than twice as much energy best molecular explosives. The possibility developing nanoenergetic that are optimised for specific applications by controlling spatial organisation on length scales ranging from nanometres to metres is discussed. To do so a fundamental understanding relationships between structure and performance does not yet...

We describe a simplified system of laser-driven flyer plates for shock compression science and spectroscopy. used commercially available one-box Nd:YAG lasers beam homogenization solutions to create two launch systems, one based on smaller (400 mJ) YAG laser an inexpensive diffusive optic, larger (2500 diffractive homogenizer. The launch, flight, impact processes were characterized by 8 GHz fiberoptic photon Doppler velocimeter. investigated effects different substrates, adhesives,...

Broad-band multiplex vibrational sum-frequency generation spectroscopy (SFG) was used to study CO2 reduction on a polycrystalline Ag electrode with room-temperature ionic liquid (RTIL) electrolyte, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4), 0.3 mol % water. The Ag/RTIL/H2O system has been shown reduce low overpotential and, depending water concentration, Faradaic efficiency of nearly 100% (Rosen, B. A.; Salehi-Khojin, Thorson, M. R.; Zhu, W.; Whipple, D. T.; Kenis, P. J....

We investigated the shock initiation of energetic materials with a tabletop apparatus that uses km s−1 laser-driven flyer plates to initiate tiny explosive charges and obtains complete temperature histories high dynamic range. By comparing various microstructured formulations, including pentaerythritol tetranitrate (PETN) based plastic (PBX) denoted XTX-8003, we determined micron-scale pores were needed create hot spot temperatures. In where micropores (i.e., micron-sized pores) present,...

This review discusses new developments in shock compression science with a focus on molecular media. Some basic features of and detonation waves, nonlinear excitations that can produce extreme states high temperature pressure, are described. Methods generating detecting waves reviewed, especially those using tabletop lasers be interfaced advanced diagnostics. Newer methods such as shockless precompression generate cold dense matter discussed. Shock creates metallic form hydrogen, melts...