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Coulomb explosion imaging, which is the reconstruction of a molecular structure by measuring the three-dimensional momenta of atomic ions formed by a Coulomb explosion of multiply charged molecular cations (MMCs), has been utilized widely. In contrast, intact MMCs, whose properties and reactions are interesting from both fundamental and applied scientific perspectives, themselves have been little explored to date. This study demonstrates that the four-atom molecule diiodoacetylene (DIA) can survive as a long-lived species in the gas phase after the removal of four electrons in intense femtosecond laser fields. The electron configurations of the equilibrium structures of the electronic ground states calculated by the complete active space self-consistent field (CASSCF) method reveal the stability of multiply charged DIA. The dissociation energies are estimated to be 3.01, 3.59, 2.57, 1.82, and 1.61 eV for neutral, cation radical, dication, trication radical, and tetracation, respectively. A fairly deep potential well suggests that a DIA tetracation is metastable toward dissociation, whereas the repulsive potential of a pentacation radical confirms its absence in the mass spectrum. With their sufficiently long lifetimes, minimum number of atoms, and simple dissociation paths, DIA MMCs are promising candidates for further experimental and theoretical investigations of multiply charged ion chemistry.

The kinetic energy of ions produced by a Coulomb explosion, in which multiply charged molecular cations dissociate, is determined by the charge number, mass, and geometric configuration of the ions upon explosion. Although the importance of the structural deformation and migration of atoms on kinetic energy variations is well known, there has been little investigation into the effect of charge localization before the ions are released. In this study, the angular distributions of iodine and carbon ions ejected from linear alkanes, which have one iodine atom on each side of an alkyl chain having one to six carbon atoms, are measured. The highly charged iodine ions (I4+, I5+) are emitted mostly along the laser polarization direction, whereas the angular distribution of iodine ions becomes isotropic the longer the alkyl chain and the lower the charge number of iodines are. Furthermore, the longer the alkyl chain, the higher the kinetic energy of iodine and carbon ions. The emission of ions is discussed in terms of the selective ionization of aligned molecules based on their molecular orbitals. The charge localization during ionization in strong alternating electric fields followed by two-body Coulomb explosion via a C I bond cleavage is proposed.

Intense femtosecond lasers as well as X-ray free electron lasers provide new means to produce multiply charged molecular cations. The fragmentation processes that these high energy species undergo, termed Coulomb explosion, are utilized to determine the static molecular structures as well as to trace the molecular dynamics of ultrafast chemical reactions. This review focuses on recent advances made in studies of Coulomb explosion imaging, highlighting the use of this process to determine the static structures of complex molecules, geometric isomers, chiral molecules and molecular complexes. Briefly, we summarize the recent time-resolved studies of surface electric fields and the controversy pertaining to the contribution of Coulomb explosion to the mechanism for ablation of solid surfaces.

We investigated the significant differences in the angular distribution of carbon ions ejected from dimethylacetylenes (CH_3-C≡C-CH_3 and CH_3-C≡C-C≡C-CH_3) and diiodoacetylenes (I-C≡C-I and IC≡C-C≡C-I) induced by a Coulomb explosion. The longest linear chain molecule ever reported was exposed to intense femtosecond laser fields (40 fs, < 5×10^14 Wcm^-2) in this study. In the cases of the diiodoacetylenes, the angular distributions of the carbon ions were orthogonal with respect to the laser polarization direction and became narrower as the length of the molecules became longer....

Chemical reactions of metal ions in solution were studied using 800 nm, 90 femtosecond laser pulses with a laser intensity range beginning at sub-micro-Joules/pulse, where the intensities were at or just below supercontinuum generation. Products were observed as surface resonance absorptions assignable to Ag, Au nanoparticles (NPs) and light scattering, indicating the formation of Pd NPs. The consumption efficiencies of metal ions from the Au and Pd ions were estimated to be 10−3 per incident photon. The major absorbing species of the laser energy was water, which led to the formation of solvated electrons that acted as a reducing agent of metal ions, while direct multi-photon dissociation to neutral atoms was unlikely. Metal ion Fe3+and Yb3+ systems are also discussed, where Fe3+ to Fe2+ was ascribed to two-photon absorption and Yb3+ to Yb2+ to a reduction followed by solvent ionization.

This paper reveals one of the primary chemical processes in femtosecond filaments. Reduction yields from Eu3+ to Eu2+ by focused femtosecond 800 nm pulses in ethanol solution were determined to be 0.021 (Eu2+ molecule/800 nm photon absorbed) or 0.14 (micro mol/ absorbed laser energy(J)) under single filament conditions. The Eu3+ captured an electron which was formed by filamentation, leading to Eu2+. About half of the solvated electrons that initially survived were estimated to be captured by Eu3+. Halogen ions are found to make a contribution to femtosecond pulse absorption with an increasing tendency with Cl

Coulomb explosion of nonmetal ions emerged from a variety of molecules has been studied and utilized for the determination of molecular structure and reaction dynamics. In contrast, Coulomb explosion of metal ions, particularly the large Coulombic interactions are expected, has not yet been explored. In this study, the angular distributions of Mnx+ (x = 1–5), Cy+ (y = 1–4), and Oz+ (z = 1–3) emerged from dimanganese decacarbonyl, in which two metal atoms are sandwiched by axial ligands, exposed to intense femtosecond laser fields (1 × 1014–3 × 1015 W cm−2) are investigated. Manganese ions are produced at relatively low laser intensity compared with other transition metal ions with the same charge number but emerged from mononuclear complexes such as metallocenes and metal hexacarbonyls. The kinetic energies of Mn4+ and Mn5+ are described by the simple Coulomb repulsion model of manganese dimer ion. Fairly high kinetic energy of oxygen and carbon ions compared with those emerged from metal hexacarbonyls strongly suggests that atomic ions originating in ligands are repelled by manganese ions at the moment of Coulomb explosion. The use of dinuclear metal complex is advantageous in the production of multiply charged metal ions accompanying high kinetic energy since two manganese ions are in close confinement due to the repulsions with axial ligand (atomic) ions.

Metal separation by using laser-induced particle formation was applied to the recovery of Pd from a mixed solution with Mo. In this separation, the Pd ions in the mixed solution containing 1 vol% ethanol were selectively reduced by irradiation of pulsed laser (10 Hz repetition rate) and high-repetition-pulse (HRP) laser (30 kHz repetition rate) with the wavelength of 355 nm while keeping irradiation power constant. The laser-induced reduction resulted in the generation of the Pd neutrals, which is followed by the aggregation of Pd neutrals in the absence of a stabilizing agent. The generated Pd particles were recovered and separated from the Mo ions by filtration. ICP-AES analysis of the filtrate elucidated that the Pd metals were successfully separated from Mo with a high recovery efficiency (84%). The recovery efficiency of Pd was different in the irradiation between the pulsed and HRP lasers; the efficiency obtained using the pulsed laser was 12% higher than that from the HRP laser. XRD analyses demonstrated that the Pd particles subjected to pulsed laser irradiation were 30 times larger than those subjected to the HRP laser. Based on TEM observations, the sizes of the Pd primary particles were approximately 200 nm (pulsed laser) and

Ytterbium 3+ ions in alcohol were found to be reduced to the corresponding 2+ ions upon laser irradiation with a stepwise two-color two-photon excitation. The infrared (975-nm) pulse with a duration of 4 ns pumps the ground state to the 4f excited state with the transition of (2)F(5/2) ← (2)F(7/2), and the second photon (355-nm) generates the charge transfer (CT) state of Cl 3p to Yb 4f; the reduction then occurs. Laser energy and excitation wavelength dependencies well-explain the above mechanism. The product Yb(2+) was detected by its absorption spectrum peak at 367 nm. The absorption spectrum of the intermediate in the two-photon chemistry was measured from the 4f excited state ((2)F(5/2)) to the CT state by nanosecond laser photolysis. The intermediate spectrum appears in the wavelengths shorter than 400 nm with the molar extinction coefficient on the order of (10(2) M(-1) cm(-1)) at 340 nm and can be explained in terms of the CT absorption shifted by IR photon energy. A UV nanosecond laser pulse (266 nm from a YAG laser with a duration of 6 ns) can generate the reactive CT state by one-photon absorption and leads to Yb(2+) formation. The reaction yields for single-photon UV excitation and the second photon in the two-photon excitation are on the order of 0.1, suggesting that the reactive states are a common CT state.

Emerging evidence suggests that chronic exposure to DDT and its derivatives is associated with a variety of human disorders such as anemia. The present study demonstrated that p,p'-DDT caused microcystic anemia in a dose-dependent manner (0, 5, 50, and 500 ppm) in the long-term study up to 2 years. To elucidate the mechanism(s) by which p,p'-DDT induces anemia, certain hematological parameters were assessed in rats fed specific doses of p,p'-DDT for 2 weeks, and the effect of lipopolysaccharide on anemia of inflammation was also examined in p,p'-DDT-treated rats. The parameters included the content of hemoglobin per reticulocyte, mean corpuscular volume of reticulocytes and mature erythrocytes, corpuscular hemoglobin concentration mean of mature erythrocytes, and saturation levels of transferrin and iron. During the 2-week treatment period, hypochromic microcytic reticulocytes and hypochromic normocytic mature erythrocytes were observed in p,p'-DDT-treated rats, with no evidence of alteration in plasma iron levels. p,p'-DDT enhanced microcytosis of reticulocytes, as well as mature erythrocytes, which occurred due to severe hypoferremia resulting from anemia of inflammation; however, plasma iron levels were attenuated probably through the inhibition of interleukin-6. Our data suggests that long-term treatment with p,p'-DDT induces microcytic anemia, possibly because of the impairment of iron utility in erythrocytes.

We report a biphasic malignant mesothelioma in an aged female F344/DuCrlCrlj rat. Macroscopically, multiple pale brown nodules were observed in the abdominal cavity with retention of bloody ascites. Histopathologically, the tumor cells spread over the peritoneum and formed masses on the surface and underlying adipose tissues. The tumor cells dominantly proliferated in a solid, nodular or nest-like pattern with modest amount of fibrillar connective tissues, which contained hyaluronan. The tumor consisted of ovoid, polygonal or spindle-shaped cells that possessed eosinophilic cytoplasms including glycogen; some tumor cells showed a signet-ring-like structure. Multinucleated cells and mitosis were found frequently, and direct invasion to intra-abdominal organs and intravascular metastasis to the liver were observed. Immunohistochemically, keratin and mesothelin were strongly positive in most of tumor cells, while vimentin was mainly positive in spindle-shaped cells. Podoplanin was also positive, particularly in the cell membrane of tumor cells. Electron microscopically, tumor cells showed an intercellular desmosome-like structure, basement membrane and microvillus. We diagnosed the case as a malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure.

Multiple ionization and subsequent Coulomb explosion have been studied for many organic molecules and their clusters; however, the metal complexes, particularly the large Coulombic interactions expected between a metal and its ligands, have not yet been explored. In this study, the angular distribution of CO(+), oxygen, and carbon ions ejected from metal hexacarbonyls (M(CO)6, M: Cr, Mo, W) having Oh symmetry by Coulomb explosion in femtosecond laser fields (1 × 10(14) W cm(-2)) is investigated. The emissions of oxygen ions are well-explained in terms of the geometric alignment along a line inclined 45° relative to the CO-M-CO axis in a M(CO)4 plane. Unlike the explosion behavior of the oxygen ions located on the outer part of the molecule, the explosion behavior of the carbon ions was affected by the laser intensity, kinetic energy, and metal. This finding that the emission trends of carbon sandwiched between oxygen and metal atoms were the opposite of those for oxygen was explained by the obstruction by oxygen, the deformation of structure in bending coordinates, and the strong interaction with charged metal. The anisotropic Coulomb explosion of metal complexes reflecting their structural symmetry and central metal charge is a promising candidate for use in the investigation of large Coulombic interactions at the molecular level.

Several features distinguish intact multiply charged molecular cations (MMCs) from other species such as monocations and polycations: high potential energy, high electron affinity, a high density of electronic states with various spin multiplicities, and charge-dependent reactions. However, repulsive Coulombic interactions make MMCs quite unstable, and hence small organic MMCs are currently not readily available. Herein, we report that the isolated four-atom molecule diiodoacetylene survives after the removal of four electrons via tunneling. We show that the tetracation remains metastable towards dissociation because of the localization (91-95 %) of the positive charges on the terminal iodine atoms, ensuring minimum Coulomb repulsion between adjacent atoms as well as maximum charge-induced attractive dipole interactions between iodine and carbon. Our approach making use of iodines as the positively charged sites enables small organic MMCs to remain intact.

While studying a series of methyl-substituted benzenes, C 6 H 6− n (CH 3 ) n with n = 2, 3, 4, 6, and perfluorobenzene in the gas phase using 193-nm laser flash photolysis, we observed the formation of p -xylylene (benzoquinodimethane) due to the elimination of two hydrogen atoms as a result of a two-photon process. The results were explained in terms of an intermediate hot molecule formed by internal conversion which finally led to the ground electronic state. Quadratical dependencies on the photoproducts were observed for toluene, xylene, mesitylene, and perfluorobenzene in the presence of a foreign gas, while linear dependencies were observed for durene and hexamethylbenzene. Dewar-type benzene was detected from photolysis of hexamethylbenzene.

Didecyldimethylammonium chloride (DDAC) is used worldwide as a germicide, in antiseptics, and as a wood preservative, and can cause adverse pulmonary disease in humans. However, the pulmonary toxicity of DDAC has not yet been thoroughly investigated. Mice were intratracheally instilled with DDAC to the lung and the bronchoalveolar lavage (BAL) fluid and lung tissues were collected to assess dose- and time-related pulmonary injury. Exposure to 1500 μg/kg of DDAC caused severe morbidity with pulmonary congestive oedema. When the BAL fluid from survivors was examined on day 3 after treatment, exposure to 150 μg/kg of DDAC caused weakly induced inflammation, and exposure to 15 μg/kg did not cause any visible effects. Next, we observed pulmonary changes that occurred up to day 20 after 150 μg/kg of DDAC exposure. Pulmonary inflammation peaked on day 7 and was confirmed by expression of interleukin-6, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP)-1α, MIP-1β, and regulated upon activation, normal T-cell expressed and secreted in the BAL fluid; these changes were accompanied by altered gene expression of their chemokine (C–C motif) receptor (Ccr) 1, Ccr2, Ccr3, and Ccr5. Cytotoxicity evoked by DDAC was related to the inflammatory changes and was confirmed by an in vitro study using isolated mouse lung fibroblasts. The inflammatory phase was accompanied or followed by pulmonary remodeling, i.e., fibrosis, which was evident in the mRNA expression of type I procollagen. These results suggest that administering DDAC by intratracheal instillation causes pulmonary injury in mice, and occupational exposure to DDAC might be a potential hazard to human health.

Quadruply charged, neon-like silicon and helium-like carbon were generated by the exposure of hexamethyldisilane to intense femtosecond laser pulses. Dissociation of the silicon-silicon bond, the formation of highly charged silicons, as well as the saturation intensity of their formation were studied by mass spectroscopy. The production of these ions in high abundance, but also with lower laser intensity than theoretically expected for the element, was accomplished by using organosilicon compounds. Multiply charged silicon was generated at low laser intensity because stripping electrons from organosilicon compounds is much easier than from pure silicon due to the loose binding of electrons belonging to molecular orbitals. Femtosecond laser ionization is a valuable methodology for producing highly charged ions in high abundance and is useful in many fields of interest.

Fused anthracene cation and a series of anthracene-C n H m cluster-like products were observed on irradiatior with nonresonant femtosecond pulses at 1.4 μm. Ionization of polycrystalline anthracene revealed strikingly different features such as the absence of multiply charged molecular ions, the appearance of H + and C + a low intensity without the formation of C n H m fragment ions, C n H m -attached and detached molecular ions, and multimer cation formation, compared with the gas-phase experiments. The fusion reactions of anthraceno and C n H m fragments indicated the presence of novel reactions among high-density cations in the crystal produced by femtosecond laser irradiation.

A 4-week repeated dose oral toxicity study of phenobarbital (PB) sodium was conducted in F344 rats of both sexes at PB doses of 0.8, 8, and 80 mg/kg/day to fully elucidate its general toxicity including hematological changes. Both sexes in the 80 mg/kg/day group showed staggering gait, lacrimation, and/or sedation, which were more evident in the early stage of treatment. The body weight gain and food consumption were greater in these animals than in controls. Hematology revealed a significant reduction in the hematocrit (Ht), hemoglobin concentration (Hb), and erythrocyte count (RBC) in both sexes at 80 mg/kg/day, which was accompanied by a decrease in the cell mean Hb (CHCM) in mature erythrocytes with an increase in unsaturated iron binding capacity. Female rats also showed reduction in the CHCM in reticulocytes, content of hemoglobin per reticulocyte, and transferrin saturation. PB prolonged the activated partial thromboplastin time and inversely increased the platelet count with no evidence of platelet activation. Well-known toxic effects of PB on the liver and thyroid were observed in a dose-dependent manner, along with altered lipid, glucose, and electrolyte metabolism. The serum levels of PB increased dose-dependently, when examined in females received 8 and 80 mg/kg/day on day 1 and 28; there were no difference in C(max) and AUC(0-24) values between day 1 and day 28. These results indicated that PB has the potential to elicit multiple organ toxicity including an effect on the hematopoietic system. The hematological analysis provided evidence for hypochromic anemia, plausibly caused by the impairment of iron utility.

Myopericytoma is a perivascular tumor that has been recently described in humans, but not in laboratory rodents. The authors encountered an intra-abdominal tumor resembling human malignant myopericytoma in a Fischer rat. Grossly, the tumor was found as two brown-colored masses located in the mesentery of rectum. Microscopically, the tumor was composed of oval to spindle-shaped cells, which were arranged in sheets around numerous thin-walled branching vessels and partly showed a concentric perivascular growth pattern. Mitoses were frequently seen, and the tumor cells showed a local invasion. Immunohistochemically, the tumor cells were strongly positive for alpha-smooth muscle actin and weakly positive for vimentin and desmin. Ultrastructurally, the tumor cells had dendritic processes, actin-like thin filaments with dense bodies, basement membranes, hemidesmosomes, and micropinocytotic vesicles. These findings suggest that the most appropriate term for diagnosis of the present case could be a malignant myopericytoma.

We investigated the direct ionization and desorption of solid C60 by the irradiation of femtosecond nonresonant (neutral and cationic states) pulses at 1.4 µm. We concluded that ion desorption is induced by Coulomb explosion. Initially formed highly charged molecular ions were annihilated with neighboring neutral or lower-charged ions, which finally resulted in singly charged C60. The electronically and vibrationally excited hot ions were formed by the release of excess energy after the charge redistribution, electron-hole recombination, and electron impact processes leading to delayed (thermal) ionization. Singly charged ions were finally emitted due to the high density of the surface charge.

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) international validation study of in vivo rat alkaline comet assays, we examined cadmium chloride, chloroform, and D,L-menthol under blind conditions as coded chemicals in the liver and stomach of Sprague-Dawley rats after 3 days of administration. Cadmium chloride showed equivocal responses in the liver and stomach, supporting previous reports of its poor mutagenic potential and non-carcinogenic effects in these organs. Treatment with chloroform, which is a non-genotoxic carcinogen, did not induce DNA damage in the liver or stomach. Some histopathological changes, such as necrosis and degeneration, were observed in the liver; however, they did not affect the comet assay results. D,L-Menthol, a non-genotoxic non-carcinogen, did not induce liver or stomach DNA damage. These results indicate that the comet assay can reflect genotoxic properties under blind conditions.

We examined the femtosecond nonresonant ionization of organic amines with vertical ionization potentials as low as 5.95 eV. The quantitative evaluation of suppressed ionization relative to the single active electron approximation model was done by comparing the saturation intensity, I(sat), in experiments and theory. ADK theory was found to be useful in predicting the ionization yield in the I(sat) scale within a factor of 2, even for molecules with very low ionization potentials. The degree of suppression was, however, smaller than that of benzene. The localization of electrons on the nitrogen atom was found to affect the ionization behavior under the strong laser field. The delocalized pi electrons in benzene could not follow the laser field adiabatically, while those in localized molecular orbitals could. In addition, the growth of a tunneling barrier due to the screening effect in amines may be relatively smaller than that in benzene.

To clarify the knowledge and beliefs of the Japanese general population related to legal options, pain medications, communication with physicians, and hydration/nutrition in end-of-life care, and to explore the associations between end-of-life care they had experienced and these beliefs, a questionnaire survey was conducted on two target populations: 5000 general population subjects and 866 bereaved family members of cancer patents who died in 12 palliative care units in Japan. The respondents were requested to report the legal knowledge about end-of-life options, pain-related beliefs, communication-related beliefs, and hydration/nutrition-related beliefs, and their experiences with end-of-life care. A total of 3061 responses were analyzed (effective response rate, 54%). The respondents were classified into six groups: no bereavement experience (n = 949), those who had lost family members within the past 10 years from noncancer diseases at institutions (n = 673), those who lost family members from noncancer disease at home (n = 264), those who lost family members from cancer at institutions other than palliative care units (n = 525), those who lost family members from cancer at home (n = 86), and those who lost family members from cancer at palliative care units (n = 548). Across groups, 32-45% and 50-63% of the respondents stated that treatment withdrawal and double effect act were legal, respectively. Between 34% and 44% believed that cancer pain is not sufficiently relieved, 27-38% believed that opioids shorten life, and 24-33% believed that opioids cause addiction. Communication-related beliefs potentially resulting in barriers to satisfactory end-of-life discussion were identified in 31-40% ("physicians are generally poor at communicating bad news") and in 14-25% ("physicians are not comfortable discussing death"). The bereaved family members of the patients who died in palliative care units were significantly more likely than the other groups to believe that cancer pain is sufficiently relieved, and significantly less likely to believe that opioids shorten life, that opioids cause addiction, that physicians are generally poor at communicating bad news, and that physicians are uncomfortable discussing death. Between 33% and 50% of the respondents, including families from palliative care units, believed "artificial hydration should be continued as the minimum standard until death," while 15-31% agreed that "artificial hydration relieves patient symptoms." A significant proportion of the Japanese general population has beliefs about legal options, pain medications, and communication with physicians that potentially result in barriers to quality end-of-life care. As their experiences in specialized palliative care significantly influenced their belief, systematic efforts to spread quality palliative care activity are of value to lessen these barriers and achieve quality end-of-life care.

DDT is known as a nongenotoxic hepatocarcinogen and has been shown to induce microsomal enzymes and GGT-positive foci and to inhibit gap junctional intercellular communication (GJIC) in the rodent liver. In consideration of these findings, we examined time-related changes in potential factors including hepatic enzyme induction, oxidative stress, cell proliferation, and GJIC in a 4-week and a 2-year feeding studies of p,p'-DDT with F344 rats. Consequently, hepatic microsomal P450 isozymes such as CYP2B1 and CYP3A2 were induced from the beginning of treatment in a dose-dependent manner. Measurement of oxidative stress markers revealed significant increases in lipid peroxide and 8-hydroxydeoxyguanosine at dose levels that induced hepatocellular tumors. Cell proliferation was enhanced within 3 days at any dose level, but returned to normal after 7 days and no significant changes thereafter. GJIC was inhibited throughout the study from the beginning to the end of treatment. Histologically, eosinophilic foci appeared earlier than controls and increased in number and size prior to development of hepatocellular tumors. These results indicate that DDT may induce eosinophilic foci as a result of oxidative DNA damage and leads them to neoplasia in combination with its mitogenic activity and inhibitory effect on GJIC. Oxidative stress could be a key factor in hepatocarcinogenesis by DDT.

Naphthalene was ionized with 130 fs pulses of different polarizations at 1.4 microm. In contrast to the results of ionization by 0.8 microm pulses, fragmentation was dramatically suppressed and naphthalene molecular ions of up to 3+ were produced. The use of this simple model of ionization and large electron kinetic energy enabled us to study the electron-recollision-induced fragmentation and/or double ionization more precisely. The failure of the theoretical prediction of ion yield for the case of naphthalene prevented us from judging the electron recollision solely by a comparison with theoretical curves. Therefore, the effects of laser polarization on the ratios between differently charged states and between molecular and total ions were compared at the same effective (peak) intensity instead of average intensity. Comparison under the same effective intensity enabled us to identify the effects of ellipticity clearly. Evidence of the electron recollision was found in the doubly charged molecular ion formation but not in the fragmentation. The single-electron recollision event was not sufficient to induce fragmentation because of its low energy transfer efficiency. We concluded that the fragmentation originated in the unstable nature of the highly charged molecular ion itself and in the Coulomb explosion in the case of naphthalene.

The two-photon chemistry of gaseous benzene was studied by laser flash photolysis using an ArF laser (193 nm) pumping to the S2 state. The major product was assigned to 1,3-hexadiene-5-yne, and one of the minor products was the phenyl radical. The formation mechanism is suggested to be as follows: hot benzene ( S 0 * * ) is formed by internal conversion from the S2 state, and hot benzene with two-photon energy ( S 0 * * * ) is formed from an excited state of S 0 * * . S 0 * * * is produced by a two-photon process, and its internal energy reaches 1243 kJ/mol. 1,3-Hexadiene-5-yne can form at rates much faster than the collision frequency (∼1010 s−1) under benzene 0.53 kPa in the presence of 51 kPa of propane. Collisional cooling is expected to quench the slow processes from S 0 * * as well as the decomposition of 1,3-hexadiene-5-yne. 1,3-Hexadiene-5-yne and the phenyl radical can be the primary products of the two-photon fragments, which have been found by a multimass ion imaging technique.

Purpose To clarify the bereaved family's perceptions about the appropriateness of timing when physicians first referred patients to palliative care units, and to identify the factors contributing to family-perceived late referrals. Subjects and Methods A multicenter questionnaire survey was conducted on 630 bereaved family members of cancer patents who were admitted to palliative care units in Japan. A total of 318 responses were analyzed (effective response rate, 62%). Results Half of the bereaved family members regarded the timing of referrals to palliative care units as late or very late, while less than 5% of families reported early referrals (very late [19%, n = 59], late [30%, n = 96], appropriate [48%, n = 151], early [1.6%, n = 5], and very early [2.2%, n = 7]). Multiple regression analyses revealed that the independent determinants of family-perceived late referrals were: family belief before admission that palliative care shortens the patient's life, insufficient in-advance discussion about preferred end-of-life care between patients/families and physicians, families' insufficient preparation for changes of patient conditions, and hospital admission before referrals. Conclusion In Japan, the timing of referrals to palliative care units was late or very late from the families' perspectives. The independent determinants of family-perceived late referrals were: family misconception about palliative care, inadequate communication with physicians, and families' insufficient preparation for deterioration of patients' conditions. Systematic strategies to overcome these barriers would contribute to providing appropriate palliative care at all stages of cancer.

Coulomb explosion of hexa-fluorobenzene in an intense laser field (1.0 × 10 16 W cm −2 ) was investigated using time-of-flight (TOF) mass spectrometry. The fluorine ions were mainly ejected parallel to the laser polarization, whereas the carbon ions were broadly distributed. The angular distribution features were totally different from those of benzene. Molecular dynamics simulations indicated that the substitution of fluorine atoms and/or ions caused ultrafast deformation of the carbon framework during the explosion. The effect of molecular alignment induced by the intense laser field is discussed.

Anthracene molecule was ionized with 130-fs pulses at two wavelengths, 0.8 and 1.4 μm. Anthracene ionized at 1.4 μm showed predominance of molecular ions with only few fragment ions, whereas excitation with 0.8-μm pulse produced many fragment ions. These observations are explained in terms of non-resonant (1.4 μm) vs. resonant (0.8 μm) excitations with the electronic levels of anthracene cation.

A series of alkylarenes (AR) was excited by an ArF excimer laser in the gas phase. The neutral radical was observed by transient absorption spectroscopy without traces of emission, triplet state, or cation radical. Single and multiphoton (up to three-photon) processes were observed even though molecules have similar structures. This presents a quite different feature from ordinary photochemistry in the condensed phase. Neutral radical production was explained well by the hot molecule mechanism and compared with statistical reaction theory. The differences between multiphoton reactions in the condensed phase and those in the gas phase were discussed.

The ionization and fragmentation of 2,3-dimethyl-1,3-butadiene of a femtosecond laser have been studied at various pulse durations, which were changed from 35 fs to 1 ps. A reflectron-type time of flight mass spectrometer (TOF-MS) was used for ion detection. Molecules were ionized under a strong laser field and formed parent ions. Some were fragmented, resulting in a drastic increase of ionic species. Fragmentation was dominant when a long duration pulse was used, probably because the parent and large fragmented ions were further decomposed into small fragmented ions. Such heavy fragmentation may cause an underestimation of Isat.

We detected parent and fragment ions from 14 chlorinated and a few fluorinated compounds as well as dibenzo-p-dioxin (dioxin) in intense laser fields. The irradiation pulse had an intensity from 1 × 1013 to 1 × 1015 W cm-2, with a 130-fs pulse duration at a central wavelength of 800 nm. Irradiation at this intensity led to a singly ionized species and a small amount of atomic ions, indicating the onset of Coulomb explosions. We have previously reported finding a key factor in determining the parent and/or fragment ion formations of organic hydrocarbons with an intense femtosecond laser pulse [Harada, H.; et al. Chem. Phys. Lett. 2001, 342, 563−570]. This key factor is a requirement for parent ion predominance if the excitation laser wavelength and the absorption spectra of the target cation are in nonresonance, and vice versa. Use of this factor has been found to be effective for molecules other than hexachlorobutadiene. The threshold intensities Isat at the infinity ionization rate were determined and ar...

Coulomb explosions of benzene induced by an intense femtosecond laser field were investigated by time-of-flight (TOF) mass spectrometry at a laser intensity of 8.0×1016 W cm−2, with a pulse width of 120 fs. The multiply charged ions of Cq+ (q=1–4) and H+ were detected, and their energies were found to be distributed in the range of 0–160 eV. The explosions were concluded to be anisotropic because the kinetic energies of multiply charged carbon ions are highly parallel to the laser electric field. Molecular dynamics simulations, including the effects of tunnel ionization, electron recombination, and the spatial configuration of benzene for laser electric fields, were performed to elucidate the kinetic-energy distributions and the dynamics of exploded benzene ions. The results of the simulations reproduced the essential points of observation concerning the energies and distributions of the ions in the TOF experiments. The simulations suggest that the charge-hopping processes enhance ionization, finally leading to an anisotropic explosion, which events are similar to those found in the case of C60 explosions. Furthermore, our findings have strongly suggested that time evolution of the hopping greatly depends on spatial configuration in the case of planar molecule benzene.

Cyclophane derivatives were irradiated with an ArF excimer laser in the gas phase. No triplet states, fluorescence, or cation radicals were observed in the transient spectra. The CH 2 -CH 2 bonds dissociated, forming corresponding xylylenes by a two-photon process. The bond dissociations were explained in terms of a multiphoton reaction of hot molecules formed by an internal conversion. In addition, a slow rise of xylylene that originated in the single photon dissociation process of hot cyclophane was observed in the case of methyl-substituted paracyclophanes under low pressure conditions. The specific reaction rates of the dissociations of highly strained paracyclophanes were well explained by a statistical reaction theory, if a simple consideration of strain energy was made in the calculations.

Two pairs of organic molecules (2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene; 1,4-cyclohexadiene, 1,3-cyclohexadiene) were irradiated with a high-intensity 120-fs laser pulse in the intensity region of 10 14 W cm −2 . One molecule in each pair had no allowed electronic transition in the cation at the excitation wavelength of 800 nm, resulting in parent ion dominance. In contrast, the counter molecule, which had a similar structure but with absorption in the cation at the excitation wavelength, showed heavy fragmentation with a negligibly small signal of the parent ion. The previously reported observations are explainable on the basis of the proposed mechanism for fragmentation in femtosecond ionization.

Recent experimental and computational studies on intense short-pulse-laser interactions with small objects such as molecules (C60) and clusters are reviewed. An anisotropic Coulomb explosion of C60 was observed, on irradiation by a high-intensity laser pulse (1×1016 W/cm2). The energy distributions of Cq+ ions (q=1–4) (distributed over 1 keV) generated from the explosion process were characterized, with their dependence on laser polarization. These results are qualitatively explained by classical molecular-dynamics simulation. It was clearly established that the crucial process for the anisotropic Coulomb explosion is not electron impact ionization, but cascade hopping of electrons. An analytical model and three-dimensional particle simulations of intense laser interaction with a cluster of overdense plasma are presented. When the laser intensity is above a critical value, it blows off all electrons from the cluster and forms a non-neutral ion cloud. During the Coulomb explosion of the ion cloud, ions acq...

The hot molecule (S0**) is in a highly vibrationally excited state formed by rapid internal conversion from initially prepared electronic excited states. The importance and predominance of the S0** mechanism in VUV gas phase photochemistry has been demonstrated. In this account, the fundamental physicochemical properties of S0** are discussed in order to understand the characteristic features of S0** reactions, and VUV laser chemistry is reviewed from the following two points of view: 1) The generalization and classification of VUV chemistry for a variety of molecules, including the hot molecule mechanism and other competitive mechanisms; 2) A new strategy of multiphoton chemistry that employs hot molecule as an intermediate. Internal conversion is a dominant deactivation process for many molecules in the VUV region. Aromatic hydrocarbons and olefins are the representative examples of S0** reactions. However, fluorescence and intersystem crossing are major deactivation processes in some cases such as larg...

Some quinolinol derivatives possessing suitable triplet state energy were examined to sensitize the luminescence of neodymium ion (Nd(III)) as coordinating ligands. Photosensitized luminescence in the near-infrared region of four neodymium(III) complexes: tris(8-quinolinolato)neodymium(III) ([Nd(q)3]), tris(5,7-dichloro-8-quinolinolato)neodymium(III) ([Nd(Clq)3]), tris(5,7-dibromo-8-quinolinolato)neodymium(III) ([Nd(Brq)3]) and tris(5,7-diiodo-8-quinolinolato)neodymium(III) ([Nd(Iq)3]), were observed by selective excitation of the ligand moieties in DMSO-d6. Highly efficient intramolecular energy transfer from the excited ligand moieties to the central Nd(III) ion was successfully achieved by using the halogenated ligands.

C60 vapor was irradiated with an intense femtosecond laser pulse (1×1016 W/cm2 in 120 fs at a wavelength of 800 nm). Multiply charged carbon ions, up to C4+, were detected in the time-of-flight spectra. We have measured both energy and angular distributions with respect to the laser polarization direction for ions with different charge number. The kinetic energy of ions are distributed above 1 keV. The angular distribution measurement shows that the highly charged ions of C3+ and C4+ are mostly distributed in the directions parallel to the laser polarization, and the C+ ions are slightly distributed in the direction perpendicular to it. These observations clearly indicate that an anisotropic explosion takes place. The average energy of ions with the different charge number is found to be proportional to the square of the charge number, while the maximum energy is proportional to the charge number. Classical molecular dynamics simulations have been successfully carried out reproducing not only the energy s...

A Coulomb explosion in a benzene molecule induced by an intense femtosecond laser field has been studied using the method of time-of-flight mass spectrometry. The laser intensity region of a Ti:sapphire laser was from 2.9×10 16 to 1.8×10 17 W cm −2 . Major ions were found to be multiply-charged carbon atoms, while the ion intensities of benzene fragments were small. The initial kinetic energy releases of C q + ( q =1∼4) ions increased with increases in laser intensity, reaching 330 eV for the C 4+ ion at 1.8×10 17 W cm −2 . A critical structure of the Coulomb explosion, where the charges are non-uniformly distributed and the structures are expanded slightly, has been postulated to explain such great energies of the multiply-charged ions.

Luminescence of Nd(III) in an organic solvent having C-H bonds was achieved for the first time by complexing Nd(III) with long-chain perfluoroalkylated ligands such as bis(perfluorooctylsulfonyl)aminate (pos). The complex [Nd(pos)(3)] gave an emission quantum yield of 3.0+/-0.5 % in undeuterated acetone. The bulky pos ligands suppress the excitation of C-H vibrations, energy migration at diffusional collision, and the coordination of acetone molecules (see picture) to the Nd(III) center, which otherwise quench the luminescence.

Photosensitized luminescence in the near-infrared region of five low vibrational β–diketonato neodymium(III) complexes, tris(1,1,1,5,5,5-hexafluoroacetylacetonato)neodymium(III) (1), tris(4,4,5,5,5-pentafluoro-1-pentafluorophenyl-1,3-pentanedionato)neodymium(III) (2), tris(4,4,5,5,6,6,6-heptafluoro-1-pentafluorophenyl-1,3-hexanedionato)neodymium(III) (3), tris(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluoro-1-pentafluorophenyl-1,3-decanedionato)neodymium(III) (4), and tris[bis(pentafluorobenzoyl)methanato]neodymium(III) (5), were examined by the selective excitation of the ligand moieties in THF-d8. The intramolecular energy transfer efficiencies from the excited ligands to the central Nd(III) ion were determined and the order of 1

Multiphoton reduction of Eu3+ to Eu2+ in methanol was induced by irradiation with the second harmonic (394 nm, 2 ps) of a Ti:sapphire laser. The conversion efficiencies were increased to 0.3 for short pulse excitation, as compared to on the order of 10-5 for a nanosecond dye laser pulse. It appears that a three-photon process pumps a deep charge-transfer state from which Eu3+ efficiently dissociates to Eu2+. On the basis of the excitation spectra, the first intermediate state is the 5L6 state, which is one of the f-electronic excited states. The Eu2+ concentration increased shot by shot and approached a plateau. The saturation behavior will be explained in terms of the back photooxidation of Eu2+ to Eu3+.

Optical field ionization is potentially useful for molecular analysis. A molecule is efficiently ionized to theparent and multiply charged ions, and eventually atoms in highly charged states are produced. Ultrafast timeresolvedx-ray diffraction techniques are emerging as powerful ways to observe the dynamics and structures ofchemical as well as biological reactions. These two promising applications developed by a terawatt laser arereviewed in brief.

Formation of the metal particles of Cd has been studied by nanosecond laser flash photolysis using an ArF excimer laser with the oscillation wavelength of 193 nm. The sample was a 10% methanol solution of CdCl2. The solvated electron, eaq−, was generated by the excitation of charge transfer bands of Cl− to solvent. The eaq− efficiently reduced Cd2+ to Cd+ during a laser pulse of 30 ns (FWHM). The Cd particles were produced by the reaction between Cd+ and Cd+. In the air saturated solution, the Cd+ was easily oxidized by dissolved oxygen. The concentration of the Cd particles formed in the degassed solution was approximately twice of that in the air saturated solution.