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Intramolecular interactions of face-to-face tetrathiafulvalenes (TTFs) in 1,8-bis(tetrathiafulvalenyl)naphthalene frameworks were investigated in neutral and cationic states. From X-ray analysis an...

The conformational property of ethoxybenzene has been investigated by means of the laser-jet spectroscopy and the theoretical calculations. The quantum-mechanical analysis of the two-dimensional potential surfaces for the S 0 and S 1 states that have been obtained from the DFT and TDDFT calculations, respectively, has been carried out. Its result suggested the existence of the second conformer ( gauche ) in addition to the main conformer ( trans ) in the both states, and it was predicted that the 0–0 band of the gauche conformer would appear at about 400 cm −1 lower than that of the trans conformer. The S 1 ← S 0 fluorescence excitation spectrum of jet-cooled ethoxybenzene has been measured. The peak that is assignable to the 0–0 band of the second conformer has been observed, whose spectral position (red-shifted from that of the trans conformer by about 229 cm −1 ) is qualitatively consistent with the theoretical prediction.

The ground and low-lying excited states of Na(NH3)n and Na(H2O)n (n = 1–8) clusters were studied using ab initio molecular orbital methods. The calculated vertical transition energies to the 32P(Na)-type states agree well with the energies of the absorption maxima. The clusters change from a valence state to a two-center state via a diffuse one-center state with increasing n in both the ground and excited states. The localization of an unpaired electron proceeds at a faster rate against n in Na(H2O)n than in Na(NH3)n. The formation of an excited state of the solvated electron is found in Na(H2O)4–8.

We propose a series of carbon nanostructures in the shape of tetrapod as a kind of three-dimensional junction for carbon nanotubes. The tetrapod junctions are such open networks that are made of sp2 carbon atoms only, have negative Gaussian curvature, and connect four nanotubes together. We define the structure of standard tetrapod junctions, the simplest one, that have 12 heptagons other than hexagons and have the Td symmetry.Our tight-binding energy-band calculations for the standard tetrapod junctions of smaller sizes show that their electronic property mainly depends on one particular topological factor: the junctions having a carbon atom in the center of each triangular face of tetrahedron exhibit metallic band structure while the junctions having a benzene ring in the center of the faces are semiconductors. We also find that tetrapod junctions connecting (6,0) nanotubes exhibit a flat band near the Fermi energy in a particular momentum region. The origin of the flat band states can be figured out from the wavefunction distribution. We also show the possibility to extend the standard tetrapod junctions to some non-standard ones that can connect nanotubes of different kinds and/or radii.

New optical emission spectra of linear carbon molecules, polyynes C2nH2 (n = 5–8), were observed upon UV-laser excitation of the 0–0 band of the dipole-allowed transition, 1 Σ u + ← X 1 Σ g + , of size-separated polyyne molecules in hexane. The emission spectra of C10H2 showed distinct peaks at 436 and 480 nm with a separation of ∼2100 cm−1 for a stretching vibration of the sp-carbon chain. Weak absorption features were also recorded in near-UV regions in shorter wavelengths to compare with the emission spectra. The spectral features in the emission were assigned to the vibronic bands of the forbidden electronic transition, 1 Δ u → X 1 Σ g + .

Photoelectron spectroscopy (PES) of Na 2 - (H 2 O) n (n ≤ 6) was investigated to examine the solvation of sodium aggregates in small water clusters. The PES bands for the transitions from the anion to the neutral ground and first excited states derived from Na 2 (1 1 Σg + ) and Na 2 (1 3 Σ u + ) shifted gradually to the blue, and those to the higher-excited states correlated to the 3 2 S + 3 2 P asymptote dropped down rapidly to the red and almost degenerated on the 1 3 Σ u + -type band at n = 4. Quantum chemical calculations for n up to 3 showed that the spectra can be ascribed to structures where one of the Na atoms is selectively hydrated. From the electron distributions, it is found that the Na - -Na+(H 2 O) n - -type electronic state grows with increasing cluster size, which can be regarded as a sign of the solvation of Na 2 - with ionization of the hydrated Na.

The dependence of fluorescence depletion on the relative polarizations of pump and erase beams is investigated for a sample of randomly oriented Rhodamine-6G molecules. The significance of polarization effects is illustrated for two existing systems of fluorescence depletion super-resolution microscopy: a circular polarization setup, and an azimuth-linear polarization setup.

Intermolecular magnetic interactions through hydrogen bonding of the carboxy group for dimers of allyl, benzyl, and chlorinated benzyl radicals have been investigated as model systems by the ab initio molecular orbital (MO) and density functional theory (DFT) calculations. It is found possible to propagate magnetic interaction through hydrogen bonding, although the effect is small. The spin densities of π- and σ-electrons have shown that antiferromagnetic coupling exists between the two intermolecular oxygen atoms in the ground state. This behavior is consistent with McConnell’s model, being applied to the planar configuration of the two hydrogen-bonded carboxy groups.

The lowest electronically excited state of small Na(H2O)n clusters has been investigated experimentally and theoretically. The excitation energy as determined by the depletion spectroscopy method drops from 16 950 cm−1 for the sodium atom down to 9670 cm−1 when only three water molecules are attached to the Na atom. For larger clusters the absorption band shifts back towards higher energies and reaches 10 880 cm−1 for n=12. The experimental data are compared to quantum-chemical calculations at the Moeller–Plesset second-order perturbation and multireference single and double excitation configuration interaction levels. We found that the observed size dependence of the transition energy is well reproduced by the interior structure where the sodium atom is surrounded by water molecules. The analysis of the radial charge distribution of the unpaired electron in these interior structures gives a new insight into the formation of the “solvated” electron.

The potential energy surfaces of PhOH–(NH3)0,1 and NH4(NH3)1–4 have been investigated theoretically by ab initio methods. Intermolecular stretching in PhOH–NH3 assists in the radical cleavage of an OH bond occurring through a ππ*/πσ* potential crossing. Thus, excited state hydrogen transfer (ESHT) is expected to take place by a solvent-assisted mechanism even in the larger PhOH–(NH3)n. Because sufficient energy is obtained by ESHT from PhOH–(NH3)n (ππ*) to PhO–NH4(NH3)n−1 (πσ*) (n⩽5), hydrogen relocation and/or ammonia migration in the product NH4(NH3)n−1 can readily follow ESHT, which is responsible for observing isomer bands in the absorption spectra of the photoinduced reaction products of PhOH–(NH3)n.

Photodissociation spectra of Mg+(NH3)n (n=1–4) cluster ions are examined in the wavelength region of 240–1200 nm. From the comparison with the results of ab initio calculations for the structure and the excitation energies of these clusters, the observed absorption bands are assigned to the transitions derived from the 2P–2S transition of Mg+ ion. The extensive redshift of the observed spectra is ascribed to the formation of a one-center ion-pair state. In the photolysis of Mg+NH3, NH3+ and Mg+NH2 ions are produced via photoinduced charge transfer and intracluster reaction processes, respectively, in addition to the Mg+ ion generated by the evaporation of ammonia molecules. For n=2, both the intracluster reaction and evaporation are dominant decay processes, while the evaporation is the sole photodissociation channel for larger clusters. The branching fractions of these processes are found to depend strongly on the solvation number n and also on the photolysis wavelength. The energetics and the dynamics o...

The vibrational spectra of phenol/ammonia clusters (1:2–5) in S0 and those of their photochemical reaction products, (NH3)n−1NH4 (n=2–5), which are generated by excited-state hydrogen transfer, have been measured by UV–IR–UV ion dip spectroscopy. The geometries, IR spectra and normal modes of phenol-(NH3)n (n=1–5) have been examined by ab initio molecular orbital calculations, at the second-order Moller–Plesset perturbation theory level with large basis sets. For the n=2 and 3 reaction products, similar vibrational analyses have been carried out. From the geometrical information of reactants and products, it has been suggested that the reaction products have memories of the reactant’s structure, which we call “memory effect.”

Picosecond time-resolved IR spectra of phenol–(NH3)3 have been measured by UV–IR–UV ion dip spectroscopy for the first time. It was found that the time-evolution of two vibrational bands at 3180 and 3250 cm −1 is different from each other. The results show that two transient species are generated from the photo-excited phenol–(NH3)3 cluster. From ab initio calculation, the transient species are assigned to two isomers of (NH3)2NH4.

We have investigated geometries, ionization potentials (IPs), and vertical transition energies (VTEs) of NH 4 ( NH 3 ) n (n=0–4) cluster radicals by ab initio MO method at the correlated level. The structures in which NH4 donates as many NH bonds as possible to the hydrogen bonding with surrounding NH3 molecules are the most stable for each n. The calculated IPs agree well with experiment. The spatial expansion of the unpaired electron occurs with stepwise solvation. The growing one-center Rydberg-like nature of the cluster radicals results in the successive decrease in the transition energies to the low-lying excited states, which is responsible for the red shifts of the electronic absorption bands.

The IR spectra of carbazole and carbazole−(H2O)n(n = 1−3) clusters in a supersonic jet have been measured by IR dip spectroscopy. The spectra show clear vibrational structures of both the monomer and the clusters in the 2900−3800 cm-1 frequency region. The observed vibrational bands are assigned to the NH stretch of carbazole and the OH stretches of H2O molecules in the clusters. The geometries and IR spectra of carbazole−(H2O)n clusters were calculated at the HF/6-31G and B3LYP/6-31++G(d,p) levels. From a comparison of the observed and calculated IR spectra, the structures of the cluster have been determined.

In connection with the recent photoelectron spectroscopy of negatively charged Na atom in ammonia clusters, the geometries, electronic state, vertical detachment energies, and harmonic frequencies of [Na(NH3)n]− (n=1–4) have been studied by the ab initio MO method. Structures having as many Na–N bonds as possible becomes more stable than other isomers as n grows. The Na 3s electrons are widely spread and delocalized in space outside the [Na(NH3)n]+ core for n⩾2. The dramatic redshifts of the photoelectron band for the 32P-type transition with increasing n reflect the electronic change from an atomic state to one-center Rydberg-type states in the neutrals. The frequencies of the combined vibrations of the NH3 ν1 mode are nearly degenerate and are expected to coalesce into only one strong IR band in the NH stretch region irrespective of n.

Geometries, vertical detachment energies (VDEs), and IR spectra of [Na(H2O)n]- (n = 1−4) have been investigated by an ab initio MO method at the correlated level. Water molecules are bound to Na- via Na−H as well as hydrogen-bond interactions. The calculated VDEs are in good agreement with the recent photoelectron spectroscopy, and all observed bands are assignable to the 32S(Na)−31S(Na-) and 32P(Na)−31S(Na-) type transitions perturbed by hydration. They are shifted to higher energy with increasing n by keeping their separation almost unchanged, which reflects the hydration structure of Na-. We also report the calculated IR spectra that are informative about the ionic Na−H bonds and the hydrogen-bond network among water molecules in the clusters.

The geometries, energetics, and vertical detachment energies of Na 2 - (NH 3 ) n (n = 0-6) were examined by ab initio molecular orbital methods in connection with their photoelectron spectra. One of the Na atoms is selectively solvated in the most stable structures for each n. The solvated Na is spontaneously ionized and the formation of a solvated electron occurs with increasing n, giving rise to the Na - -Na + (NH 3 ) n (e - )-type state. The ground and two lowest-lying excited states derived from the 1 1 Σ g + , 1 3 Z u + , and 1 3 Π u states of Na 2 , respectively, are of ion-pair character though the 1 3 Σ u + -type state has an intermediate nature slowly changing to the radical-pair state with increasing n. On the other hand, the higher states stemming from the 1 1 Σ u + , 1 3 Σ g + , and 1 1 Π u states of Na 2 show a developing radical-pair nature as n increases. The size dependences of the photoelectron spectra such as the near parallel shifts of the first and second bands, as well as the rapid red shifts of the higher bands, are studied on the basis of the electronic change of the neutrals by solvation.

The potential-energy curves of the ground and low-lying excited states for Mg(+)NH(3) along the N-H distance were examined by the ab initio configuration interaction method. The photoinduced hydrogen elimination reaction found by the recent experiment is considered to occur via the ground-state channel. The geometries, energetics, and electronic nature of the ground-state Mg(+)(NH(3))(n) and MgNH(2) (+)(NH(3))(n-1) (n=1-6) were also investigated by second-order Møller-Plesset perturbation theory and compared with those of the corresponding hydrated species. In contrast to Mg(+)(H(2)O)(n), the successive solvation energies of Mg(+)(NH(3))(n) become as large as those of MgNH(2) (+)(NH(3))(n-1) containing the Mg(2+)-NH(2) (-) core for n=5 and 6, because of the growing one-center ion-pair state with the Mg(2+) and the diffuse solvated electron. As a result, the solvation energies of the MgNH(2) (+)(NH(3))(n-1) are insufficient to overcome the huge endothermicity of Mg(+)(NH(3))--MgNH(2) (+)+H, even at these sizes, which is responsible for no observation of the H-loss products, MgNH(2) (+)(NH(3))(n-1).

The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV-near-IR-UV-UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n = 3 cluster, while three isomers are observed simultaneously for n = 4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels.

The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250cm−1, it was found that two isomers of hydrogenated ammonia radical cluster ∙NH4(NH3)2 coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of ∙NH4(NH3)2; a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, ∙NH4–NH3–NH3, and (2) the metastable product isomerizes successively to the most stable product, NH3–∙NH4–NH3. The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9ps, respectively.The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250cm−1, it was found that two isomers of hydrogenated ammonia radical cluster ∙NH4(NH3)2 coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of ∙NH4(NH3)2; a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, ∙NH4–NH3–NH3, and (2) the metastable product isomerizes successively to the most stable product, NH3–∙NH4–NH3. The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9ps, respectively.