Morihisa Saeki

Use of a long-duration ns pulse for efficient emission of spectral lines from the laser ablation plume in water

The effect of pulse duration upon the line profile of Cu I emission observed by laser ablation of a copper metal plate immersed in water has been examined. By irradiating a pulse with the duration longer than 40 ns the spectral profile with clear narrow emission lines of Cu atoms is obtained, while the emission spectra always suffer from broadening and self-absorption by the irradiation of the 20 ns pulse for the ablation. The results show that the use of a long-duration pulse enables in situ elemental analysis of the solid surface in contact with a bulk liquid.

Hydrogen transfer in photo-excited phenol'ammonia clusters by UV-IR-UV ion dip spectroscopy and ab initio molecular orbital calculations. II. Vibrational transitions

The electronic spectra of reaction products via photoexcited phenol/ammonia clusters (1:2–5) have been measured by UV-near-IR–UV ion dip spectroscopy. Compared with the electronic spectra of hydrogenated ammonia cluster radicals the reaction products have been proven to be (NH3)n−1NH4 (n=2–5), which are generated by excited-state hydrogen transfer in PhOH–(NH3)n. By comparing the experimental results with ab initio molecular orbital calculations at multireference single and double excitation configuration interaction level, it has been found that the reaction products (NH3)n−1NH4 (for n=3 and 4), contain some isomers.

Infrared dip spectra of photochemical reaction products in a phenol/ammonia cluster: examination of intracluster hydrogen transfer

Abstract The vibrational transitions of the photochemical reaction products in phenol-(NH 3 ) 3 have been measured by infrared (IR) dip spectroscopy. Two sharp bands at ∼3200 cm −1 and a broad band in the region 2700∼3100 cm −1 are observed. The spectrum is clearly different from that of the cluster in S 0 , and also largely different from the IR spectrum of NH 4 + (NH 3 ) 2 . This suggests that hydrogen transfer occurs in electronically excited phenol-(NH 3 ) 3 . Evidence of hydrogen transfer has also been found in phenol-(NH 3 ) 4 based on the mass spectrum and the IR dip spectrum of the cluster.

IR-dip and IR-UV hole-burning spectra of jet-cooled 4-aminobenzonitrile-(H2O)1. Observation of π-type and σ-type hydrogen-bonded conformers in the CN site

Abstract The IR-dip spectra and IR–UV hole-burning spectra of jet-cooled 4-aminobenzonitrile–water 1:1 complex have been measured to investigate the effects of the introduction of two substituents into the aromatic ring on the hydrogen-bonding interaction and stable structures of the complex. We have obtained a clear evidence for the observation of three structural isomers by comparing the experimental IR spectra with the theoretical ones. The water molecule is bonded to the NH 2 site in isomer I, where the amino group can act as a proton donor and the amino hydrogen is bonded to the oxygen atom of water. Water is bonded to the CN site in isomers II and III. The structure of isomer II is very similar to benzonitrile–(H 2 O) 1 , where the water hydrogen is bonded to the cyano nitrogen and the oxygen atom of water is bonded to the ortho hydrogen atom. The water hydrogen is linearly hydrogen-bonded to the cyano nitrogen in isomer III. The intermolecular hydrogen bond in isomer II is σ-type, whereas that in isomer III is π-type. The proton-donor conformer in the NH 2 site and the σ-type linear conformer in the CN site have not been observed in the aniline–(H 2 O) 1 and benzonitrile–(H 2 O) 1 complexes, respectively. The observation of three stable structures has been successfully explained by atomic charges on the constituent atoms obtained by natural population analysis.

Electronic isomers in [(CO2)nROH]− cluster anions. I. Photoelectron spectroscopy

Photoelectron spectra of [(CO2)n−1ROH]− (R=H and CH3) with 2⩽n⩽7 have been measured at a photon energy of 4.66 eV. Analysis of the photoelectron band envelopes has revealed that the spectra of [(CO2)n−1H2O]− with 3⩽n⩽5 consist of two band components. The maximum of each component corresponds to the vertical detachment energy (VDE) of the relevant anionic species. In each spectrum the VDE values for the two components differ by ≈1 eV. For example, the [(CO2)4H2O]− spectrum is characterized by two VDE values of 2.63±0.04 and 3.71±0.06 eV. From the VDE difference, we conclude that the observed two components arise from isomers having different electronic structures, and that these “electronic isomers” can be designated as C2O4−⋅H2O(CO2)n−3 and CO2−⋅H2O(CO2)n−2. Coexistence of electronic isomers occurs also in [(CO2)n−1CH3OH]−, but only at n=3. The [(CO2)n−1CH3OH]− anions with n≠3 display photoelectron spectra composed of a single broad band, which corresponds to photodetachment from CO2−⋅CH3OH(CO2)n−2 struct...

Electronic isomers in [(CO2)nROH]− cluster anions. II. Ab initio calculations

Ab initio MO calculations have been performed for the [(CO2)nROH]− (R=H and CH3) anions with n=1 and 2. Three stable structures are found for [(CO2)H2O]−, and two structures for [(CO2)CH3OH]−. All the [(CO2)ROH]− structures are characterized by the charge localization on the CO2 moiety, which interacts with ROH through an O–H⋯O linkage. It is also revealed that the addition of ROH to CO2− leads to the formation of a potential barrier against autodetachment higher than that of a bare CO2−, which results in the increasing stability of [(CO2)ROH]− species. For n=2 the calculations predict the existence of two types of isomers having different degrees of the excess electron localization: CO2−⋅ROH(CO2) and C2O4−⋅ROH isomers. These “electronic isomers” are calculated to be close in energy, while their calculated vertical detachment energies (VDEs) differ by more than 1 eV. The ab initio results are discussed in comparison with recent experimental ones derived from photoelectron spectra of [(CO2)nROH]−.

Theoretical Study on the Structure and the Frequency of Isomers of the Naphthalene Dimer

The structures of the naphthalene monomer and dimer were investigated with performing vibrational analysis. The MP2 optimization showed that the naphthalene monomer has a nonplanar geometry in the 6-31G, 6-31G*, 6-31+G*, and 6-311G basis sets, while it has a planar geometry in the 6-31G*(0.25) and Dunnings correlation consistent basis sets. The MP2/cc-pVDZ calculation showed the presence of the four stable isomers, which were part of the isomers in the previous MP2/6-31G* calculation (Walsh, T. R. Chem. Phys. Lett. 2002, 363, 45). The presence of extra structures in the MP2/6-31G* calculation is attributed to a poor description of the potential energy surface, which is evident from the nonplanar structure of the monomer in the MP2/6-31G* calculation. The relative stability among the isomers in the MP2/cc-pVDZ calculation without counterpoise correction was maintained in both the single-point calculation at the MP2/aug-cc-pVDZ//MP2/cc-pVDZ level and the counterpoise-corrected optimization at the MP2/cc-pVDZ level. The relative stability among the isomers suggested an enhancement of the π-π interaction in the structure with lower symmetry, which could be explained using a molecular-orbital model. The vibrational analysis in MP2/cc-pVDZ without the counterpoise correction suggested that the isomers of the naphthalene dimer were distinguishable by the observation of the infrared spectrum in the low-frequency region (150-600 cm(-)(1)).

Electronic and infrared spectra of jet-cooled 4-aminobenzonitrile-H2O. Change of NH2 from proton acceptor to proton donor by CN substitution

Abstract The electronic and infrared spectra of jet-cooled 4-aminobenzonitrile–(H2O)1 (4ABN–(H2O)1) hydrogen-bonded complex have been measured by the resonance-enhanced multiphoton ionization (REMPI) and infrared-dip (IR-dip) spectroscopy. Both the amino and cyano groups form intermolecular hydrogen bond with water, providing two stable isomers. It has been found that the substitution of the CN group at the para-position of aniline changes the electronic nature of the amino group in the S0 state from a proton acceptor to a proton donor.

Ab initio study of (CO2)n−: structures and stabilities of isomers

Abstract The geometrical structures and stabilities of (CO 2 ) n − with the size range 3⩽ n ⩽6 are investigated by ab initio calculations including the effects of electron correlation. The calculations have shown that the structures of (CO 2 ) n − can be formulated by either CO 2 − ·(CO 2 ) n −1 or C 2 O 4 − ·(CO 2 ) n −2 , and that the geometry of the (CO 2 ) 2 − dimer remains more or less in all the optimized structures. In all the sizes investigated in the present study, the most stable isomers are of the C 2 O 4 − ·(CO 2 ) n −2 form, being consistent with the results obtained in photoelectron spectroscopic studies.

Structural Evolution of (1-NpOH)n Clusters Studied by R2PI and IR Dip Spectroscopies

A large-size 1-naphthol cluster, (1-NpOH)(n), with n ≤ 30 was prepared by using a high-pressure pulsed valve. The electronic and vibrational transitions of (1-NpOH)(n) with n = 3-9 were measured by resonant two-photon ionization (R2PI) and ion-detected IR dip spectroscopies. The S(1) ← S(0) R2PI spectrum shows partially resolved structures around the origin band in the (1-NpOH)(n) cluster with n = 3-8. The (1-NpOH)(3) and the (1-NpOH)(6) clusters show relatively sharp origin bands. The structure of (1-NpOH)(3) was determined by comparison of the IR dip spectrum with the simulated one by DFT calculation, while those of (1-NpOH)(n) (n ≥ 4) were discussed in terms of topological geometries of a hydrogen-bonded network. Those analyses suggest that (i) the (1-NpOH)(3) cluster has the cyclic structure where three 1-NpOH monomers are linked by both the hydrogen-bonding and the π···C-H interaction between naphthyl rings and (ii) the (1-NpOH)(n) cluster with n ≥ 4 is built up by attaching the 1-NpOH monomers to the (1-NpOH)(3) core.