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Relation between the optical detection of NMR signals by the Faraday and Cotton–Mouton effects in fluids and nuclear spin–spin coupling tensors is theoretically explored. An expression is derived for nuclear-spin-induced optical Cotton–Mouton (NSIOC-M) effect from molecules with the prepolarized nuclear magnetic moments. That contains two parts. The temperature independent part is related to hypermagnetizability due to the nuclear magnetic moments. The temperature dependent part is proportional to product between nuclear spin–spin coupling tensors and anisotropy of molecular polarizabilities. NSIOC-M effect can give information on molecular structures in fluids, such as bond lengths and angles. Order of magnitude of the new effect are estimated.

This Letter studies intensity relation between IR–UV doubly resonant sum-frequency vibrational spectra (DR-SFVS) and antisymmetric resonant vibrational Raman scattering, and gives an approximate expression of their intensity ratio. Based on the intensity ratio expression and the related experimental data of IR and antisymmetric resonant vibrational Raman spectra, hypothetical DR-SFVS of ferrocytochrome c has been sketched. The experimental investigation on IR–visible DR-SFVS of ferrocytochrome c may be a test of the related theory.

Under the adiabatic approximation, antisymmetric resonant vibrational transition polarizabilities for even-electron systems with the ground and excited vibronic states belonging to the real representations have been deduced to be zero by the time-reversal symmetry and group theory. Beyond the adiabatic approximation the non-adiabatic corrections to them are non-zero, particularly in the degenerate or near degenerate electronic states, such as Jahn–Teller and pseudo Jahn–Teller cases where adiabatic approximation breaks down. The results verify Buckingham’s conjecture of non-zero antisymmetric transition polarizabilities beyond the adiabatic approximation in 1988. The conclusions of this letter agree with the experiments of antisymmetric vibrational Raman scattering. The compact expressions for the non-resonant and resonant antisymmetric transition polarizabilities are given in the Appendix.

The CCSD(T)/11e-RECP//MP2/11e-RECP method was used to explore the potential energy surfaces (PESs) of the formation of Ag n ( n = 2–6) clusters. Two kinds of reaction mechanisms were revealed in the formation of Ag n clusters, the association mechanism for the formation of Ag 2 , Ag 5 , and Ag 6 clusters and the association–isomerization mechanism for the formation of Ag 3 and Ag 4 clusters. Based on the canonical transition state theory, the calculated rate constants of the formation of Ag n clusters displayed an odd–even effect: the rate constants of formation of Ag n clusters with odd number were larger than those with even number. The rate constant of formation of Ag 4 was the lowest, whereas that of Ag 5 was the highest among Ag n ( n = 2–6) clusters. The formation of Ag 4 was the most difficult step in the aggregation process of the silver clusters. The formation of Ag 4 may be related with the critical point in the silver aggregation process.

The ground-state geometries of dilithium and monolithium complexes of phthalocyanine (Li2Pc and LiPc) and three reduced/oxidized species of LiPc (i.e., [LiPc]−, [LiPc]2− and [LiPc]+) have been studied with the density functional theory. It was shown that Li2Pc has a stable D4h structure with the two lithium atoms bonded symmetrically up and below the Pc plane. Both LiPc and [LiPc]− have a planar D4h structure whereas [LiPc]+ has a significantly saddle-distorted D2d structure. [LiPc]2− has a planar D2h structure with a rectangular distortion due to the ground state Jahn–Teller effect. Electronic absorption spectra of Li2Pc and LiPc were calculated with the time-dependent DFT method, and the results are in good agreement with the experiments.

The ground-state geometry, electronic structures and vibrational frequencies of alkali metal porphyrin complexes, M2P (M=Li, Na, K), have been studied using B3LYP/6-31G(d) method. The computed structures were compared with the crystallographic data of related compounds. The Na2P and K2P molecules have D4h symmetry with the two alkali metal atoms locating on the different sides of the porphyrin plane. For Li2P, the energy of D4h structure is higher than the symmetry broken C2h structure, but the energy difference is very small. Natural population analysis suggests a significant charge transfer from the alkali metals to the porphyrin ring.The vibrational frequencies of M2P (M=Li, Na, K) were calculated and the results were compared with zinc porphyrin (ZnP).

The potential energy surface for the decomposition of methyl hypochlorite (CH 3 OCl) is calculated using G2MP2 theory. Geometries, vibrational frequencies, IR intensities and relative energies for various stationary points have been determined. The obtained vibrational frequencies and IR intensities for CH 3 OCl are in good agreement with the experimental values. The calculated reaction heats are also in accord with the available data in the literature. Among the unimolecular decomposition paths of CH 3 OCl, the formation of HCl and CH 2 O is suggested to be the major one.

The influence of the hyperfine interaction on laser-induced shifts in electron spin resonance spectra is investigated and calculated, taking the sodium atom as an example. As the incident laser frequency is near-resonant, the different hyperfine lines may produce distinguishable shifts which may be important for the application of the effect to practical analysis.

Taking a paramagnetic transition metal complex ion [IrBr 6 ] 2− as an example, the laser-induced ESR shifts in oriented and unoriented samples have been studied and calculated. In oriented and unoriented systems the ESR shifts result from the contribution of the symmetric and antisymmetric polarizabilities. The shifts of the [IrBr 6 ] 2− complex ion are calculated to be of the order of 1∼10 kHz for a laser beam of 10 W cm −2 . The factors affecting the magnitude of the laser-induced ESR shift are discussed. The results indicate that there should be observable ESR shifts in a molecular or radical paramagnetic system on applying linearly or circularly polarized light at a frequency near optical absorption.

This paper studies the contribution of the magnetically perturbed symmetric polarizability to the laser-induced shift in electron spin resonance (ESR) spectra. The calculated ESR shift for a sodium atom as an example shows that in a circularly polarized laser beam at a frequency near the optical absorption the ESR shift due to the contribution of the symmetric polarizability becomes one order of magnitude larger than that of the antisymmetric part. In a linearly polarized optical field only the symmetric part contributes to the laser-induced ESR shift. The shift of a sodium atom near optical absorption will be of the order of 1–10 MHz.

The contribution of antisymmetric nonresonant vibrational Raman scattering to the totally symmetric ν 16 and ν 17 bands of tetrahydrofuran is theoretically and experimentally studied. In nonresonant Raman spectra, the depolarization ratios of ν 16 and ν 17 combination bands with pseudorotation have been found to be ρ ∼ 0.75, far larger than those of ordinary totally symmetric vibrational bands. By using time-reversal symmetry and group theory, theoretical results show that the antisymmetric transition polarizabilities induced by pseudorotation-vibronic coupling make an important contribution to the depolarization ratios of the ν 16 and ν 17 bands and become one order of magnitude smaller than or the same order of magnitude as the symmetric ones.

Antisymmetric resonant vibrational Raman scattering is studied using time-reversal symmetry. Under the Born-Oppenheimer approximation, for even-electron systems with the ground and the excited vibronic states belonging to real representations, the antisymmetric resonant Raman transition polarizabilities are strictly zero due to time-reversal symmetry. Only if the ground or the resonant excited vibronic states of an even-electron system belong to E representations of groups C n , C n h or S n ( n ⩾ 3), or for an odd-electron system, can the antisymmetric vibrational resonant Raman transition polarizability be nonzero. The results explain the inconsistency between the space symmetry prediction and the experimental facts of antisymmetric resonant Raman scattering.

Surface-enhanced Raman-scattering (SERS) spectra and ultraviolet visible (UV) absorption spectra of meso-tetrakis (4-sulfonatophenyl)porphine (TSPP) adsorbed on Ag 2 O colloids and their changes with time are reported in this paper. The spectral features reveal that the adsorbed TSPP molecules undergo a metal incorporation process on the Ag 2 O surface, and a surface complex Ag(II)TSPP is finally formed. A reaction intermediate in the process of the metal incorporation, called the “sittingatop” (SAT) complex, was proposed on the basis of SERS and UV spectra.

The enhanced fluorescence and enhanced Raman spectra of dye-1555 molecules adsorbed on silver chloride sols are detected for the first time. The enhanced fluorescence is attributed to the double resonance effect proposed by Chew and Wang. The enhanced Raman spectra indirectly support the energy-transfer model of spectral sensitization of dyes, one of two competing mechanisms of spectral sensitization in the photographic process.

Surface-enhanced Raman scattering (SERS) spectra from pyridine, 1,4-dioxane and the dye 1-ethyl-3′-methyl-2-thiacyanine iodide molecules adsorbed on α-Fe 2 O 3 colloids have been recorded. The enhancement factor for pyridine was estimated to be about 10 4 . The relation among the SERS, the colloid absorption spectra and the colloid aggregation was established. The SERS enhancement from these molecules adsorbed on α-Fe 2 O 3 colloid was found to be similar to that on Ag colloids.