[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.

/pdf/gaussian-basis-sets-for-use-in-correlated-molecular-2mfmi3165a.pdf

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.

/pdf/design-of-organic-molecules-with-large-two-photon-absorption-28jm5nxpc3.pdf

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.

/pdf/optical-gas-sensing-a-review-4uaf589xiq.pdf

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

Symmetry-breaking collisional energy transfer in the 4νCH rovibrational manifold of acetylene: spectroscopic evidence of a quasi-continuum of background states

Cavity ringdown (CRD) absorption spectroscopy provides high sensitivity and photometric precision in the measurement of weak optical absorption spectra. We report several innovations in CRD technique involving either pulsed or continuous-wave (cw) tunable coherent sources. In the former case, we use narrowband, injection-seeded optical parametric oscillator (OPO) devices based on quasi phase-matched nonlinear-optical media and a novel intensity-dip cavity control scheme; one such pulsed OPO is pumped by a compact, in expensive multimode laser but still delivers single-mode OPO signal output. The latter area concerns cw-CRD spectroscopy with a single-mode tunable diode laser (TDL) and a rapidly swept ringdown cavity, most recently enhanced by a novel optical heterodyne approach that yields a noise-limited absorption sensitivity of 3 × 10−9 cm−1. Such pulsed and cw CRD methods are used to record weak rovibrational spectra of carbon dioxide gas (CO2) with high resolution in the 1.5-μm near-infrared region. Emphasis is on high-performance spectroscopic systems with relatively simple, in expensive, compact instrumentation.

Cavity Ringdown Spectroscopy: New Approaches and Out Comes

The magnitudes of dipole moment and molar Kerr constant of 1,2-dichloroethane as solute in carbon tetrachloride, previously recorded by Aroney, Izsak, and Le Fevre, are discussed in relation to internal rotation in the molecule. The results are found to be consistent with a mixture consisting of 31.3% of gauche-isomer and 68.7 % of trans-isomer. Estimation of the potential energy barriers restricting intramolecular rotation is attempted and the results found to be satisfactory.

Internal rotation in 1, 2-dichloroethane

A β-barium borate optical parametric oscillator (BBO OPO) serves as the tunable source for coherent anti-Stokes Raman spectroscopy (CARS). Two variants of this approach are devised to make rotationally resolved CARS measurements of nitrogen in air. In the scanned CARS technique, the BBO OPO operates in its continuously tuned, narrow-band mode with injection-seeding control of OPO signal wavelength. In the other technique, a free-running BBO OPO is used for single-shot, multiplex CARS measurements.

Rotationally resolved coherent anti-Stokes Raman spectroscopy by using a tunable optical parametric oscillator

Time‐resolved infrared‐ultraviolet double‐resonance (IRUVDR) spectroscopy is used to look for rotationally specific channels in collision‐induced vibrational energy transfer between the ν6 and ν4 modes of D2CO. The efficiency of such V‐V transfer has been shown in previous work to be enhanced by a combination of Coriolis coupling and rotor asymmetry. IRUVDR spectra, recorded in pure D2CO vapor with a range of delay intervals between IR pump and UV probe laser pulses, reveal (J,Ka) ‐dependent propensities in the resulting ν6→ν4 transfer arising from D2CO/D2CO collisions. At the same time, rotational relaxation within the rovibrational manifold (v6=1) initially prepared by the IR pump laser is found to be more pronounced than the growth of population in the neighboring v4=1 manifold, due to ν6→ν4 transfer. This trend is shown to be reversed in the case of D2CO/N2O collisions, where the effects of rotational relaxation appear to be less pronounced than those of ν6→ν4 transfer. This work, performed with spect...

Brian J. Orr

Papers

Symmetry-breaking collisional energy transfer in the 4νCH rovibrational manifold of acetylene: spectroscopic evidence of a quasi-continuum of background states

Cavity Ringdown Spectroscopy: New Approaches and Out Comes

Internal rotation in 1, 2-dichloroethane

Rotationally resolved coherent anti-Stokes Raman spectroscopy by using a tunable optical parametric oscillator

Rotationally specific mode–to–mode vibrational energy transfer in D2CO/D2CO collisions. I. Spectroscopic aspects