In this review the basic principles of interference lithography (IL) are described. IL is emerging as one of the most powerful yet relatively inexpensive methodologies for creating large-area patterns with micron-to sub-micron periodicities.-dimensional periodic structures ( ) can be obtained by interfering ( ) non-coplanar beams in a photoresist. The symmetry and shape of the "unit cell" can be conveniently controlled by varying the intensities, geometries, polarizations, and phases of the beams involved. IL done with shorter wavelength lasers and/or liquid immersion lithography can create features with sub-50 nm dimensions. Such periodic structures are beginning to find wide use in photonic crystal science, optical telecommunications, data storage, and the integrated circuit industry. Newer innovations such as diffraction element assisted lithography or DEAL and phase-controlled IL for making twodimensional structures are also discussed.SEM images of two-dimensional patterns created by three-beam non-coplanar interference lithography. The upper left hand image corresponds to the case when the phases of the three beams used to make the exposure are equal. The remaining images correspond to situations where one laser beam has been given a different phase relative to the other two beams when making the exposure.

Clusters of methanol and ethanol formed above neat liquid samples were entrained in a supersonic jet of helium and probed in the expansion using 118 nm vacuum ultraviolet laser single-photon ionization/time-of-flight (TOF) mass spectrometry. Almost every cluster ion observed in the TOF mass spectra could be represented by the formula H(ROH)n+, where R=CH3 or C2H5, and n=1–5. Formation of these species is attributed to a well-established ionization pathway where each protonated (n−1)-mer originates from its n-mer neutral parent. Signals in the TOF mass spectra due to the protonated trimers H(CH3OH)3+ and H(CH3CH2OH)3+ were found to be the most intense and provides direct evidence that these particular cluster ions are “magic-number” structures. The possible relationships between the observed ion data and the neutral cluster vapor phase distributions are discussed. In this context, methanol and ethanol vapor cluster distributions at 298.15 K and at several pressures⩾the equilibrium vapor pressure were computed using the grand canonical Monte Carlo and molecular dynamics techniques. Lastly, differences between these experiments and the results of bimolecular reaction studies are discussed.

A possible switching mechanism has been investigated for nonlinear photonic crystals doped with an ensemble of non-interacting three-level nanoparticles. In this scheme, an intense pump laser field is used to change the refractive index of the nonlinear photonic crystal while a weaker probe field monitors an absorption transition in the nanoparticles. In the absence of the strong laser field the system transmits the probe field when the resonance energy of the nanoparticles lies near the edge of the photonic band gap due to strong coupling between the photonic crystal and the nanoparticles. However, upon application of an intense pump laser field the system becomes absorbing due to a band edge frequency shift that arises due to a nonlinear Kerr effect which changes the refractive index of the crystal. It is anticipated that the optical switching mechanism described in this work can be used to make new types of photonic devices.

Resonance and preresonance Raman spectra are obtained from chromium-containing argon matrics. Two progressions are assigned to Cr2 and Cr3, the former with optical constants ω″e=427.5 and ω″ex″e=15.75 cm−1 and the latter with ω″e=313 and ω″ex″e=2 cm−1. When not in resonance two other lines at 123 and 226 cm−1 were observed and ascribed to the bending and asymmetric stretching vibration of Cr3, while the vibration forming the progression was taken to be the symmetric stretch. From this, Cr3 is deduced to be a molecule with C2v symmetry but with an apical angle near 60°, suggesting that it is perhaps a Jahn–Teller distorted D3h molecule.

Clusters of butanol formed above neat liquid samples were entrained in a supersonic jet and probed using 10.5 eV vacuum ultraviolet laser single-photon ionization/time-of-flight mass spectrometry. The four different isomers of butanol (n-butanol, sec-butanol, iso-butanol, and tert-butanol) were studied separately to assess the influence of the structure of the alkyl chain on the formation and stability of the hydrogen bonded clusters. Most of the higher mass features observed in the mass spectra could be assigned to protonated alcohol clusters, H(ROH)n+, n⩽3; R=C4H9, that arise from facile proton-alkoxy radical/alkoxide anion dissociation. Signals due to protonated trimers were only evident in the spectra of tert- and sec-butanol. Empirical force fields, density functional theory and ab initio methods were used to identify the geometries of all clusters up to the pentamers for the different isomers. Monte Carlo simulations established vapor-phase cluster distributions, while molecular dynamics was used to assess the relative stability of the isomeric tetramers. Together, these experimental and theoretical results suggest that butanol tetramers are “magic-number” structures, and that the protonated ion signals of size n could be correlated with the neutral cluster of size n+1, provided the vapor pressures sampled in the supersonic jet exceeded equilibrium values.