Chemically induced dynamic electron polarization (CIDEP) generated through interaction of the excited triplet state of 1-chloronaphthalene, benzophenone, benzil, and Buckminsterfullerene (C60) with 2,2,6,6,-tetramethyl-1-piperidinyloxyl (TEMPO) radical was investigated by using time-resolved ESR spectroscopy. We carefully examined what factors affect the CIDEP intensities. By comparing CIDEP intensities of TEMPO in the 1-chloronaphthalene, benzophenone, and benzil systems with that obtained in the C60−TEMPO system, the absolute magnitude of net emissive polarization was determined to be −2.2, −6.9, and −8.0, respectively, in the units of Boltzmann polarization. In the 1-chloronaphthalene−TEMPO system, the viscosity effect on the magnitude of net polarization was studied by changing the temperature (226−275 K) in 2-propanol. The emissive polarization was concluded to result from the state mixing between quartet and doublet manifolds in a radical−triplet pair induced by the zero-field splitting interaction of the counter triplet molecule. The magnitude of net polarization is much larger than the polarization calculated with the reported theory that the CIDEP is predominantly generated in the region where the exchange interaction is smaller than the Zeeman energy. Our experimental results are quantitatively explained by the theory that the CIDEP is generated predominantly in the regions where the quartet and doublet levels cross. We propose a theoretical treatment to calculate the magnitude of net polarization generated by the level crossings in the radical−triplet pair mechanism under highly viscous conditions and perform a numerical analysis of the net RTPM polarization with the stochastic-Liouville equation. The viscosity dependence of the net polarization indicates that the back transition from the doublet to quartet states sufficiently occurs in the level-crossing region under highly viscous conditions. The estimated large exchange interaction suggests that the quenching of the excited triplet molecules by TEMPO proceeds via the electron exchange interaction.

The bound–bound excitation spectrum of the NO–Ar van der Waals complex associated with the NO A 2Σ+–X 2Π transition has been measured by the resonance enhanced two-photon ionization (RE2PI) method using a time-of-flight (TOF) mass spectrometer. The van der Waals bands characterized by red-shaded rotational contours present no regularity in the progression. The photodissociation action spectra obtained by probing the NO A 2Σ+(v′=0, N′=1–8) products have also been measured, and the binding energies (D0) of the complex in the A 2Σ+ and X 2Π states are determined as 44 and 88 cm−1, respectively. The action spectrum corresponding to the NO A 2Σ+(v′=0, N′=1 and 2) product shows several shape resonance peaks, which implies that the intermolecular potential between NO A 2Σ+ and Ar has a potential barrier of about 24 cm−1.

[1] Temporal and latitudinal variations of vertical profiles of N 2 O isotopomers were observed in the stratosphere over Japan (39°N, 142°E), Sweden (68°N, 20°E) O were nearly constant in the lower stratosphere (less than $22 km) but increased at higher altitudes ($22-35 km) while showing seasonal and latitudinal differences. Enrichment factors during the photolysis and photo-oxidation of N 2 O were also obtained in laboratory experiments and compared with those observed. We found that in the higher-altitude region (1) fractionation of the isotopomers is mainly determined by photolysis, but is also affected by physical processes, (2) subsidence of air masses in the winter polar vortex induces the intrusion of an upper stratospheric air mass depleted in N 2 O, and (3) decay of the vortex in the local spring leads to rapid horizontal advection of midlatitude air masses. At lower altitudes, isotopomer ratios are determined by photolysis, photo-oxidation, and the mixing of air masses within the stratosphere or between the stratosphere and the troposphere. Secular trend of isotopomer profiles was not detectable over Japan during 11 years. Assuming that the lower stratospheric air over midlatitudes is exchanged with the troposphere, isotopomer ratios of the N 2 O ''back-flux'' from the stratosphere were estimated. These values can be used in the isotopomeric mass balance model to constrain the global N 2 O budget.

Infrared spectra of OH-(H2O)n (n = 1, 2) isolated in solid Ne were measured by FT-IR spectroscopy. Complexes of OH-(H2O)n were prepared by vacuum ultraviolet (VUV) photolysis of water clusters, and the OH radical stretch and HOH bending vibrations of OH-H2O and OH-(H2O)2 complexes were identified with the aid of quantum chemical calculations. Observation of the recombination reaction OH-H2O + H --> (H2O)2 under dark conditions provides undisputed evidence for our spectroscopic assignment. Quantum chemical calculations predict the cyclic structure to be the most stable for OH-(H2O)2 and OH-(H2O)3. The strength of the hydrogen bond within OH-(H2O)n depends on cluster size.

The reactions O('D)+HCI->OH+CI (1a) and OCI+H (1b), O('D)+DCl->OD+CI (2a) and OCI+D (2b), and 0(,D)+CI 2->OCI+CI (3) are studied at an average collision energy of 7.6, 7.7, and 8.8 kcal/mol for (1), (2), and (3), respectively. H, D, and CI atoms are detected by the resonance-enhanced multiphoton ionization technique. The average kinetic energies released to the products are estimated from Doppler profile measurements of the product atoms. The relative yields [OCI+H]/[OH+CI] and [OCI+D]/[OD+CI] are directly measured, and a strong isotope effect (HID) on the relative yields is found. The fine-structure branding ratios [Clep,d/[C1(2P 3/2)] of the reaction products are also measured. The results suggest that nonadiabatic couplings take place at the exit channels of the reactions (la) and (2a), while the reaction (3) is totally adiabatic.

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Matrix isolation infrared spectroscopy has been applied to study an ozone-water complex of atmospheric interest. The complex was identified in the spectral region of three normal modes of ozone and water. Ab initio calculation at MP4(SDQ), QCISD, and CCSD(T) levels indicates the existence of only one stable conformer, which accords with the present experimental result. This conformer belongs to the Cs symmetry group where two molecular planes of ozone and water are perpendicular to the Cs symmetry plane. The binding energy was calculated to be 1.89 kcal/mol at the CCSD(T)/6-311++G(3df,3pd)//CCSD(T)/6-311++G(d,p) level of theory. The formation constant and atmospheric abundance of the ozone-water complex are estimated using the thermodynamic and spectroscopic data obtained.

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