Showing papers by "Richard J. Saykally published in 2001"
TL;DR: Detailed terahertz laser vibration-rotation-tunneling spectra and mid-IR laser spectra are compiled for several isotopomers of small (dimer through hexamer) water clusters to quantify the structures, force fields, dipole moments, and hydrogen bond rearrangement dynamics in these clusters.
Abstract: Extensive terahertz laser vibration-rotation-tunneling spectra and mid-IR laser spectra have been compiled for several isotopomers of small (dimer through hexamer) water clusters These data, in conjunction with new theoretical advances, quantify the structures, force fields, dipole moments, and hydrogen bond rearrangement dynamics in these clusters This new information permits us to systematically untangle the intricacies associated with cooperative hydrogen bonding and promises to lead to a more complete molecular description of the liquid and solid phases of water, including an accurate universal force field
748 citations
TL;DR: In this article, ultraviolet lasing from single zinc oxide nanowires is demonstrated at room temperature, and near-field optical microscopy images quantify the localization and divergence of the laser beam.
Abstract: Ultraviolet lasing from single zinc oxide nanowires is demonstrated at room temperature. Near-field optical microscopy images quantify the localization and the divergence of the laser beam. The linewidths, wavelengths, and power dependence of the nanowire emission characterize the nanowire as an active optical cavity. These individual nanolasers could serve as miniaturized light sources for microanalysis, information storage, and optical computing.
428 citations
TL;DR: In this article, the first results from studies of liquid water microjets by soft X-ray absorption spectroscopy are presented, showing that a fine-structure pattern very similar to that found for gaseous water monomers is observed when the surface-selective total ion yield (TIY) is measured, but a broadened and blue-shifted spectrum emerges when detecting the bulk-sensitive total electron yield (TEY).
Abstract: We present the first results from studies of liquid water microjets by soft X-ray absorption spectroscopy. Near the oxygen K-edge (∼530 eV) a fine-structure pattern very similar to that found for gaseous water monomers is observed when the surface-selective total ion yield (TIY) is measured, but a broadened and blue-shifted spectrum emerges when detecting the bulk-sensitive total electron yield (TEY). TIY EXAFS measurements produce a nearest neighbor O−O distance for surface molecules (3.00 A) slightly longer than that of the isolated water dimer (2.98 A), whereas the O−O distance extracted from TEY EXAFS corresponds to that accepted for bulk water (2.85 A). Together, these results evidence an equilibrium liquid water surface dominated by water molecules interacting weakly at longer distances than in the bulk, thus supporting predictions from computer simulations.
165 citations
TL;DR: The complete set of pyrene cation IR emissions is observed, with relative intensities consistent with astrophysical observations, supporting the proposal that ionized PAHs are major contributors to the UIR bands.
Abstract: We report the first observation of infrared emission from a gaseous ionic polycyclic aromatic hydrocarbon (PAH), the pyrene cation, over the range of wavelengths spanned by the ubiquitous interstellar unidentified infrared emission bands (UIRs). The complete set of pyrene cation IR emissions is observed, with relative intensities consistent with astrophysical observations, supporting the proposal that ionized PAHs are major contributors to the UIR bands. Additionally, unidentified features possibly arising from dehydrogenated PAH species are noted in the spectrum.
92 citations
TL;DR: In this article, the equilibrium constant for water dimerization (KP) was determined as a function of temperature via rigorous calculation of the canonical (H2O)2 partition function using the recently developed split Wigner pseudo-spectral method and the VRT(ASP-W) pair potential.
Abstract: The equilibrium constant for water dimerization (KP) was determined as a function of temperature via rigorous calculation of the canonical (H2O)2 partition function using the recently developed split Wigner pseudo-spectral method and the VRT(ASP-W) pair potential. Our KP(T) values are significantly larger than those from previous theoretical treatments but somewhat smaller than literature experimental values, which exist, however, only over a very limited temperature range. These results indicate that water dimers can exist in sufficient concentrations (e.g., 1016 cm-3 at 40 °C and 100% relative humidity) to affect physical and chemical processes in the atmosphere.
88 citations
TL;DR: In this paper, the authors used fluorescence near-field scanning optical microscopy (NSOM) to examine films of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) that were prepared in different ways.
Abstract: It is becoming increasingly clear that the way in which a conjugated polymer film is cast affects the interactions between polymer chains and thus the optical and electrical properties of the film. Given that conjugated polymer films cast in different ways also show different nanometer-scale surface topographies, the question that arises is: What is the correlation between surface topography, local chain packing, and the local electronic properties of a conjugated polymer film? In this paper, we address this question using fluorescence near-field scanning optical microscopy (NSOM) to examine films of poly(2-methoxy-5-(2‘-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) that were prepared in different ways. The spatially resolved photoluminescence (SRPL) spectra collected on top of the nanometer-scale topographic features (“bumps”) exhibited by spin-cast MEH-PPV films show an enhancement of the red portion of the emission relative to spectra collected from flat regions of the film. Moreover, photooxidativ...
84 citations
TL;DR: These are the first experiments that provide a detailed molecular picture of the respective motions without extensive interpretation of tau(H) on intermolecular motions for liquid water via computer simulations.
Abstract: The effect of exciting each of the three classes of intermolecular vibrations on the hydrogen bond lifetime (τH) of the isolated water trimer is investigated by far-infrared laser spectroscopy. Single excitation of a librational vibration decreases τH by 3 orders of magnitude to τH = 1−6 ps, comparable to the time scale of a number of important bulk water dynamical relaxation processes. In contrast, excitation of translational or torsional vibrations has no significant effect (τH = 1−2 ns). Although such a dependence of τH on intermolecular motions has also been proposed for liquid water via computer simulations, these are the first experiments that provide a detailed molecular picture of the respective motions without extensive interpretation.
42 citations
TL;DR: In this paper, the authors described the tentative detection of the triatomic pure carbon chain molecule, CCC, in absorption toward the Galactic center source Sgr B2 by observing the R(2) bending vibration-rotation transition (0, 1 1,0 0, 0 0, 0) near 65.7 cm 1 during one of the last flights of KAO.
Abstract: We describe more fully our original tentative interstellar detection of the triatomic pure carbon chain molecule, CCC, in absorption toward the Galactic center source Sgr B2. C3 was detected with the Kuiper Airborne Observatory (KAO) by observing the R(2) bending vibration-rotation transition (0, 1 1 ,0 0, 0 0 , 0) near 65.7 cm 1 during one ) R ( of the last flights of KAO. The R(2) absorption line detected toward Sgr B2 is centered at 63.7(5) km s 1 , with km s 1 and a peak absorption of 18(3)%. This original tentative interstellar detection of C 3 DV(FWHM)p 8.3(9) has recently been confirmed by J. Cernicharo et al. through observation of a total of nine absorption lines, including the same R(2) line with the Infrared Space Observatory . We also present highly precise new laboratory measurements of 10 rovibrational transition frequencies of the n2 bending mode of C3, which have been obtained with the Cologne Sideband Spectrometer for Terahertz Application. Subject headings: ISM: individual (Sagittarius B2) — ISM: molecules — line: identification — methods: laboratory — techniques: spectroscopic On-line material: color figure
40 citations
TL;DR: In this paper, the first direct observation of the hydrogen-bond stretching vibration for a water cluster was reported by terahertz laser vibration-rotation-tunneling spectroscopy at 142.8 cm−1 in the translational band of the liquid corresponding to the hindered translational motions of water molecules.
Abstract: We report the first direct observation of the hydrogen-bond stretching vibration for a water cluster. A perpendicular band of (D2O)3 was measured by terahertz laser vibration–rotation–tunneling spectroscopy at 142.8 cm−1 in the “translational band” region of the liquid corresponding to the hindered translational motions of water molecules. We have tentatively assigned the spectrum to transitions from the vibrational ground state to the degenerate hydrogen-bond stretch or a combination or mixed state of the degenerate stretch and a torsional vibration. Comparison with theoretical results shows that calculated frequencies are much too high, presumably because they do not include coupling between the torsional and stretching vibrations.
38 citations
01 Jan 2001
TL;DR: In this article, Saykally, Geleijns, and van der Avoird present a study on the effect of the weather on the performance of the human brain.
Abstract: $^{a}$F. N. Keutsch, M. G. Brown, P. B. Petersen, and R. J. Saykally, M. Geleijns, and A. van der Avoird J. Chem. Phys. 114 (9), 3994 February (2001).
37 citations
TL;DR: In this paper, the authors reported the first high resolution spectrum of a librational vibration for a water cluster using diode laser vibration-rotation-tunneling (VRT) spectroscopy.
Abstract: We report the first high resolution spectrum of a librational vibration for a water cluster. Four parallel bands of (H2O)3 were measured between 510 and 525 cm−1 using diode laser vibration–rotation–tunneling (VRT) spectroscopy. The bands lie in the “librational band” region of liquid water and are assigned to the nondegenerate out of plane librational vibration. The observation of at least three distinct bands within 8 cm−1 originating in the vibrational ground state is explained by a dramatically increased splitting of the rovibrational levels relative to the ground state by bifurcation tunneling and is indicative of a greatly reduced barrier height in the excited state. This tunneling motion is of special significance, as it is the lowest energy pathway for breaking and reforming of hydrogen bonds, a salient aspect of liquid water dynamics.
TL;DR: In this paper, near-field scanning optical microscopy (NSOM) images of a chemical vapor deposited (CVD) disk of zinc selenide were recorded as a function of infrared (IR) wavelengths ranging from 3.1 to 4.4 μm from an amplified femtosecond laser.
Abstract: Infrared sum-frequency generation (SFG) has been detected with near-field scanning optical microscopy (NSOM) for the first time. SFG NSOM images of a chemical vapor deposited (CVD) disk of zinc selenide were recorded as a function of infrared (IR) wavelengths ranging from 3.1 to 4.4 μm from an amplified femtosecond laser. Striation patterns, which are not observed in the topography, were detected in the optical images and exhibited increased SFG in comparison to homogeneous regions of the semiconductor. SFG images were demonstrated to have ∼ λ/20 spatial resolution in comparison to the IR wavelengths used to produce the sum frequency.
TL;DR: The mechanism of tuning fork-based shear-force near-field scanning optical microscopy is investigated to determine optimal experimental conditions for imaging soft samples immersed in liquid to obtain high feedback sensitivity and stability.
Abstract: The mechanism of tuning fork-based shear-force near-field scanning optical microscopy is investigated to determine optimal experimental conditions for imaging soft samples immersed in liquid. High feedback sensitivity and stability are obtained when only the fiber probe, i.e., excluding the tuning fork prongs, is immersed in solution, which also avoids electrical shorting in conductive (i.e., buffer) solutions. Images of MEH-PPV were obtained with comparable spatial resolution in both air and water. High optical resolution (∼160 nm fwhm) was observed.
TL;DR: In this article, the authors report the observation of a new c-type band of (D2O)3 at 583.215 GHz, which they assign to the k=±20←±10 torsional hot-band.
Abstract: We report the observation of a new c-type band of (D2O)3 at 583.215 92(37) GHz, which we assign to the k=±20←±10 torsional hot-band. The new data includes the first observation of K=0 states for the k=+10 and k=−20 levels and effects a correct assignment of these states. A new perturbation was observed for the K=2 states of the k=+20←−10 subband splitting each transition into two equally spaced equal intensity doublets. Analysis of the band and inclusion into a global fit of all torsional bands produces negligible differences with previous analyses, and confirms the validity of the Hamiltonian developed to treat the coupling between torsional motion and overall rotation. The 583.2 GHz band completes the precise characterization of all (D2O)3 vibrational levels below 100 cm−1.
TL;DR: Extensive mid-infrared lasing action by water molecules is observed in a supersonic plasma expansion contained inside an optical supercavity in this article, where an ion-electron dissociative recombination mechanism is proposed.
TL;DR: A high-resolution infrared spectrometer housing a tunable diode laser and combined with an effective laser ablation source for the cluster production has been used to study the molecular properties of small carbon clusters, reporting the first gas-phase spectrum of linear C10.
Abstract: Detected in interstellar space and as intermediates in soot formation, molecules of pure carbon in the form of linear chains or ring structures have interested researchers for several decades, who attempt to elucidate their physical properties and the processes govering their formation. A high-resolution infrared spectrometer housing a tunable diode laser and combined with an effective laser ablation source for the cluster production has been used to study the molecular properties of small carbon clusters; reported herein is the first gas-phase spectrum of linear C10.
TL;DR: In this paper, the rotational transitions of D2O with J < 12 in excited vibrational states (and the ground state) were measured with submegahertz precision in a pulsed discharge supersonic slit expansion of a D 2O/NeHe mixture while scanning the range from 1473.69 to 1685.91 GHz using the Berkeley terahertz laser sideband spectrometer.
TL;DR: The vibrational ground state of (D2O)2 has been characterized to energies as high as those of some of the intermolecular vibrations, and the first test of the VRT(ASP-W) potential at these high Ka states is presented.
Abstract: We report the observation of extensive a- and c-type rotation-tunneling (RT) spectra of (D2O)2 for Ka = 0-4. These data allow quantification of molecular constants and tunneling splittings for a number of previously unobserved RT states of (D2O)2. The vibrational ground state has thus been characterized to energies as high as those of some of the intermolecular vibrations, and we present the first test of the VRT(ASP-W) potential at these high Ka states.
01 Jan 2001
TL;DR: Groenenboom et al. as discussed by the authors used terahertz laser spectroscopy of the water dimer intermolecular velocities to estimate the rotation-tunneling levels.
Abstract: $^{a}$L.B. Braly, et al. ``Terahertz Laser Spectroscopy of the Water Dimer Intermolecular Vibrations. I. $(D_{2}O)_{2}$ II. $(H_{2}O)_{2}$'' J. Chem. Phys. 112, 10293 (2000). $^{b}$F.N. Keutsch, et al. ``Complete Characterization of the $(D_{2}O)_{2}$ Ground State: High $K_{a}$ Rotation-Tunneling Levels.'' Submitted 2000. $^{c}$G.C. Groenenboom, et al. ``Water pair potential of near spectroscopic accuracy. II. Vibration-rotation-tunneling levels of the water dimer.'' J. Chem. Phys. 113, 6702 (2000).