[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

An accurate description of the electrical properties of atoms and molecules is critical for quantitative predictions of the nonlinear properties of molecules and of long‐range atomic and molecular interactions between both neutral and charged species. We report a systematic study of the basis sets required to obtain accurate correlated values for the static dipole (α1), quadrupole (α2), and octopole (α3) polarizabilities and the hyperpolarizability (γ) of the rare gas atoms He, Ne, and Ar. Several methods of correlation treatment were examined, including various orders of Moller–Plesset perturbation theory (MP2, MP3, MP4), coupled‐cluster theory with and without perturbative treatment of triple excitations [CCSD, CCSD(T)], and singles and doubles configuration interaction (CISD). All of the basis sets considered here were constructed by adding even‐tempered sets of diffuse functions to the correlation consistent basis sets of Dunning and co‐workers. With multiply‐augmented sets we find that the electrical properties of the rare gas atoms converge smoothly to values that are in excellent agreement with the available experimental data and/or previously computed results. As a further test of the basis sets presented here, the dipole polarizabilities of the F− and Cl− anions and of the HCl and N2 molecules are also reported.

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Gaussian basis sets for use in correlated molecular calculations. IV. Calculation of static electrical response properties

A strategy for the design of molecules with large two-photon absorption cross sections, δ, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of δ. Synthesized bis(styryl)benzene derivatives with donor-π-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of δ, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide δ values in good agreement with experimental values. The combination of large δ and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.

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Design of Organic Molecules with Large Two-Photon Absorption Cross Sections

The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.

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Optical gas sensing: a review

The non-linear optical polarization of an isolated atom or molecule is treated, giving careful consideration to secular and resonant terms in the perturbation expansion. The Method of Averages introduced by Bogoliubov and Mitropolsky is used. The case where resonance-induced excited state populations are negligible, which is relevant to a wide range of non-linear optical experiments, is examined in detail for polarizations through third order in the perturbing fields. This yields concise expressions which are valid for any combination of applied field frequencies, including static fields.

Perturbation theory of the non-linear optical polarization of an isolated system

Solvent shifts of the infrared carbon-halogen stretching frequencies v(C-Hal) for a number of solutes in solution have been measured. Using chloroethane as a reference solute, a multiple regression analysis is found to correlate the relative frequency shift (Δv/v) with three independent solvent parameters: two functions of the dielectric constant and refractive index of the solvent which reflect its dipolar and non-dipolar bulk dielectric contributions, respectively, and a relative Lewis basicity parameter which allows for specific solute- solvent interactions. Solvent variation constants, which scale solvent shifts for one solute to the corresponding shifts of a reference solute according to the method of Bellamy, Hallam and Williams, have been determined and are found to be directly derivable from the regression coefficients for the solvent parameters. The possibility of further predicting solvent variation constants, in terms of linear free energy relationships for the various solutes, is discussed. Solutes examined in the course of the analysis are: chloroethane, chloromethane, chlorocyclohexane, 1-chloro-2-methylpropene, chlorobenzene, chlorobenzene[D5], 1,4-dichlorobenzene, bromomethane and iodoethane.

The effect of solute-solvent interactions on infrared carbon-halogen stretching frequencies

CO2 laser-induced chemiluminescence in SF6/hydrocarbon mixtures: Dependence on laser fluence

Spectroscopic applications of tunable optical parametric oscillators

Fast mode-to-mode vibrational energy transfer in D2CO vapour: analysis of a complex pressure dependence

Recently in this journal we presented a study of the spatial emission properties of a microwave-induced plasma (MIP). That particular study used a TM010 Beenakker cavity to generate a plasma in argon with analyte elements introduced into the plasma in a vapor form from an electrothermal (ET) atomizer. We observed that analyte emission from metallic species was localized to a narrow region at the inlet side of the plasma (i.e., at low heights in the plasma) and that no significant emission was observed higher in the plasma. These effects, together with the observation of metal deposition on the discharge tube walls and decreased analyte emission at higher microwave powers, led us to suggest that analyte atoms were being removed from the plasma before reaching the most favorable excitation region at the center of the discharge. We postulated that the loss of analyte atoms from the plasma might result after initial ionization of analyte atoms (soon after their entry into the plasma) by subsequent drift of these ions in the inhomogeneous microwave field surrounding the discharge. This present report introduces some further experimental evidence that supports the above hypothesis of analyte removal from MIP sources.

Brian J. Orr

Papers

The effect of solute-solvent interactions on infrared carbon-halogen stretching frequencies

CO2 laser-induced chemiluminescence in SF6/hydrocarbon mixtures: Dependence on laser fluence

Spectroscopic applications of tunable optical parametric oscillators

Fast mode-to-mode vibrational energy transfer in D2CO vapour: analysis of a complex pressure dependence

Further Observations on the Spatial Emission Properties of a Microwave-Induced Plasma in Argon