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Ion pair fragmentation of nitrogen molecules following Ar8+ ion collision was observed by using a position-sensitive time-of-flight method. Kinetic energy release (KER) distributions were derived from the double hit data. Higher-asymmetric fragmentation channels have peak positions of the KER higher than the Columbic value.

Summary form only given. Higher fullerenes, C/sub 76/, C/sub 78/, C/sub 82/, C/sub 84/ and C/sub 96/ were isolated from carbon soot. Their ultraviolet photo election spectra (UPS) were obtained with a synchrotron radiation light source. The UPS of their potassium complexes were also measured. The UPS of pristine fullerenes can be divided into two parts, below and above 5 eV binding energy. The region above 5 eV is /spl pi/-like electron origin and /spl sigma/-like electrons contribute to the lower region. While the upper part differs from fullerene to another fullerene, the lower part is essentially identical. This suggests isoelectronic structures of skeletal carbon cages of fullerenes. The UPS of pristine fullerenes exhibit a strong intensity oscillation when the excitation photon energy has tuned. This intensity oscillation can be interpreted in terms of difference of the azimuthal quantum numbers which is deduced from a pseudo atom treatment of fullerenes. When potassium is dosed onto fullerenes, a formation of a new peak is observed in the UPS. The location of the new peak is between the Fermi level (E/sub F/) and the first band. This is due to an electron-filling from the potassium 4s level to the lowest unoccupied molecular orbital of fullerenes. Upon potassium dosing of the higher fullerenes the UPS spectral edge moves toward E/sub F/, but it does not cross E/sub F/, which indicates their semiconductive nature.

We have experimentally investigated the relaxation dynamics of photoexcited states in semiconducting single-walled carbon nanotubes by means of femtosecond spectroscopy. The photoexcited electrons and holes are nonradiatively recombined via multi-phonon emission process within ∼1 ps . The tube diameter dependence of decay time suggests that the electron–phonon interaction is enhanced by decreasing the tube diameter.

Thermoelectric power, S ( T ), for single walled carbon nanotubes (SWNT) shows a strong curved T -dependence. The results of S ( T ) are interpreted as the effect of the interaction between conduction electrons and transition metals; i.e. Kondo effect. However, for SWNT containing alcohol molecules such as methanol or ethanol, the S ( T ) is almost proportional to T . The results indicate the characteristic metallic behavior in SWNT doped with O 2 .

Double ionization and subsequent ion-pair dissociation induced by low-energy collisions of Ar8 + were studied for various methanol isotopomers to understand how the reactions of transient methanol dications correlate with the charge states of the scattered ions. Single-hit time-of-flight (TOF) spectra of recoil ions excluding multi-hit events show that long-lived molecular dications always correlate with Ar7 + scattered ions, indicating that they are formed only by double-capture collisions that accompany transfer ionization. The double-hit TOF measurements of fragment ions show that the branching ratios of CH/OH cleaving largely depend on the charge states of scattered ions. The H/D substitution effect on the hydrogen migration indicates that a concerted motion of atoms is essential for this reaction pathway.

Instantaneous chirality induced by zero-point vibrations was observed directly by using the Coulomb explosion imaging (CEI) technique. The present results suggest the CEI would be generally applicable to diagnosis of the chirality of the isolated molecules in gas phase.

This report presents spectroscopic probes of intercalation processes in single walled carbon nanotubes. Before saturation doping of alkali metals (KC x , x∼9), we found a rather stable intermediate phase KC 27 . where the Raman active E 2g mode shows an anomalous hardening. Considering the close correlation with the graphite intercalation compounds, we postulate that in KC 27 phase, alkali ions are inserted between two tubes rather than the hollow site surrounded by three tubes.

Changes in electronic states of single-wall carbon nanotubes (SWNT) induced by chemical and electrochemical doping were investigated by optical absorption spectroscopy in the range from the visible to near infrared. When SWNT was doped with a bulky organic electron acceptor, decrease of the absorption peaks similar to that previously found for halogen doping was observed but with a relatively slower rate of decrease, reflecting different diffusion dynamics of the dopants as well as the morphology of the SWNT film. Electrochemical doping induced by the continuous shift of the electrode potential caused sequential decrease of three absorption peaks, which was explained by the sequential removal of electrons from three occupied bands in the semiconducting and metallic phase of SWNT. Implications of these results are discussed in relation to the elucidation of electronic properties of SWNT.

We have successfully synthesized single-wall carbon nanotubes encapsulating specified fullerenes (peapods) in high yield using a sublimation method. Side and section images by HRTEM indicate that almost all nanotubes are filled with high-density fullerene chains. We measured Raman spectra to estimate macroscopic yield. The observed Raman intensity of C 70 molecules in the C 70 -peapods is 1/10 of that in C 70 film, which indicates a filling rate of C 70 to be higher than 26 %. In the case of C 60 -peapods, Raman spectrum has changed rapidly by laser irradiation. Since the final spectrum at room temperature is similar to that of the orthorhombic polymer phase, a formation of one-dimensional photopolymers inside SWNTs is suggested.

New aspects of size- and state-specific properties of carbon cluster are described on the basis of experimental evidences obtained by recently developed clusterbeam apparatus. The present paper consists of mainly two topics. One of which is spin states for small carbon neutral clusters. Focusing effects induced by a hexapole magnetic field were examined for the carbon clusters from C1 to C6. The second is the study of cluster-solid surface interactions. Electron emission processes induced by collision of negative cluster ions with M0S2 single crystal were investigated in detail, paying special attention on the electron emission efficiency as functions of both size and incident kinetic energy. A new collision induced phenomenon has been found, which may be closely related with an electron detachment of negative ions induced by a surface potential of the solid target.

The existence of carbon clusters C4 and C6 with triplet electronic states has been verified from the observation of a focusing effect in a hexapole magnetic field. The present results directly show the existence of even-numbered carbon clusters with a linear chain structure.

Size selected carbon negative cluster ions (n = 5−22, 60, and 70) were examined on the collisional electron emission at solid surface as a function of the incident kinetic energy (0–1keV). Two different mechanisms were found below 1 KeV collision energy. Electron emission occurring at high energy ( > 300 eV) is totally governed by velocity of the incoming cluster ions. The electron emission at the low collision energy, on the other hand, is considerably dependent on the molecular structures of the carbon clusters, i.e., linear chain, monocyclic ring, and hollowclosed-cage structures. The latter process is a new phenomenon which may be closely related with a collisional electron detachment of negative cluster ions.

We calculated the internal energy of zinc phthalocyanine anions stored in an electrostatic ion storage ring as a function of a time after their production in a hot source. The relevant experimental data were those obtained for anions heated by a pulsed laser leading to enhancement of the delayed electron detachment signals. We evaluated the energy window of the detectable anions from the lifetime, which enable us to determine the absolute value of the internal energy.

Chain hydrocarbon anions, C4H- and C6H- extracted from a cesium sputter ion source, were stored in an electrostatic ion storage ring. The neutral species formed by electron detachment during storage were detected to measure the lifetimes of the anions. By virtue of the high sensitivity for metastable species, we found that shortlived anions with milliseconds lifetime were formed in the ion source.

The H/D isotope effect in the ion-pair dissociation processes of doubly charged methanol formed by the impact of low-energy Ar8+ was investigated. By multi-hit position-sensitive time-of-flight measurements, the branching ratios of dissociation channels yielding H, H2 or H3 fragment ions, or H/D substituted ions, and the kinetic energy release distributions of these dissociation channels were determined for methanol isotopomers.

The synthesis, isolation and preliminary characterization of all-carbon [60]fullerene dimers C121 and C122 are reported.

Magnetic susceptibility and superconductivity in exohedral fullerenes are wellknown. Advances in production and purification techniques led to macroscopic amounts of the endohedral metallofullerene LaC82. Laser desorption mass spectroscopy measurements displayed the purity of the material. In this paper we present a dc-magnetization investigation of LaC82 powder crystals. The magnetic moment as a function of temperature shows an overall paramagnetic behaviour. A signal drop can be observed at 30 K (zero field cooled curve).

Doping effects of higher fullerenes such as C 70 on electrical and optical properties of conducting polymers such as poly(3-alkylthiophene), poly(2,5-dialkoxy-p-phenylene vinylene) and poly(9,9-dialkylfluorene) have been studied and compared with those by C 60 doping. Fluorescence intensity was quenched and photoconductivity was enhanced upon doping of higher fullerenes in the conducting polymers just as the case of C 60 doping. However, there also exist differences in detailed aspects in quenching of photoluminescence and enhancement of photoconductivity between C 60 doping and higher fullerenes dopings. These results are interpreted by taking into account the electronic energy states of C 60 and higher fullerenes.

The site of La atom in La@C 82 is determined according to a C 2 -symmetry C 82 cage model. The La atom is placed under a six-membered ring which contains the C 2 axis. The nearest r (LaC) is 2.47 A. A kind of group fitting using the coordinates of C 82 cage was carried out as well as usual curve fittings. The group fitting supports the model that La atom stays at off-axis position.

We report here the first isolation and characterization of Y C[sub 82] in comparison with La C[sub 82]. The electronic structure of the major Y C[sub 82] isomer, examined by the electronic absorption spectra and the electrochemistry, is almost identical to that of the major La C[sub 82] isomer, although the ionization potentials and ionic radii of the metals are different. This indicates that Y C[sub 82]-A would have a cage structure and an oxidation state of the metal similar to those of La Cr[sub 82]-A. 15 refs., 3 figs., 1 tab.

The isomer formation of three isomers of C[sub 78] fullerene is discussed on the basis of experimental evidence revealed by pressure-controlled fullerene production. Theoretically predicted most stable isomer, C[sub 2v][prime]-C[sub 78] has been found to be very sensitive to the graphite burning condition. The fraction of C[sub 2v][prime] isomer dramatically changes from zero to 50% by changing the foreign gas pressure. The present findings strongly suggest that an isomerization within the C[sub 78] carbon network such as a pyracylene rearrangement type transformation unlikely takes place. 21 refs., 3 figs.

Heat capacity of the new compound C 60 was measured by using a laboratory-made adiabatic calorimeter between liquid helium temperature and room temperature. A phase transition phenomenon was observed as a large heat capacity anomaly extending from 180 to 260 K. The fact that the anomaly has two peaks at 250 and 255 K indicates a complicated mechanism of the phase transition and/or some effects of purity, multi-phases in the sample. The values of enthalpy and entropy of transition were estimated as 6.7 kJmol −1 and 28 JK −1 mol −1 , respectively. The normal portion of the heat capacity curve as a whole is very similar to that of graphite. In the lowest temperature region, however, the heat capacity of C 60 is much larger than that of graphite. Molecular motion in the crystal of C 60 is discussed concerning with the lattice vibrations.

Superconductivity (SC) in K-doped molecular alloys of C 60 and C 70 are studied by means of the nonresonant microwave low-field signal (LFS) and conventional ESR, and a LFS-search for SC in K x C 70 is performed. The critical temperature of K x (C 60 /C 70 ) determined at the onset of hysteretic LFS, decreases to T c =16K (at about 10% C 70 ), and T c =10K (at about 25% C 70 ), compared with T c =19K in pure K x C 60 suggesting the decrease of electron-phonon coupling. A strong multicomponent g=2 ESR signal appears and coexists with LFS at low T for SC composition of K x (C 60 /C 70 ) indicating presence of a non-SC metallic phase. At overdoping LFS disappears and a single ESR line is enormously broadened to Δ H pp (300K) = 80G. In K x C 70 doped under the same conditions the LFS is not detected, indicating absence of SC above 5K, while a narrow ESR single line appears.

X-ray diffraction (XRD) studies on single-walled carbon nanotube (SWNT) samples prepared by the arc-discharge method were reported. The XRD profile was basically explained to be a result of triangular packing of SWNTs with a lattice constant of 17.1 Å and an average nanotube radius of 7.1 Å. We found an anomalous change in XRD profiles before and after heat-treatment of the SWNT samples in air at ∼350°C. Combined with gravimetric measurements and resistivity measurements, a detailed simulation of the XRD profiles showed that air (oxygen, and/or nitrogen and/or water) can be condensed inside the SWNTs.

Ionization of triatomic molecules in collision with 120 keV Ar8+ and the subsequent molecular fragmentation has been studied by means of a position sensitive time-of-flight (TOF) technique. The triple coincidence signals for these molecules are identified for the dissociation channels of (CO2)n+ where n = 3–6. The dissociation of (NO2)n+ where n = 3–5 has also been studied. The velocity vector of each fragment ion is determined for individual collision events and the angle between the velocity vectors is calculated. For the highly ionized molecules (n = 6), the angle is consistent with the angle of the neutral molecule, both in the case of linear and bent molecules. For the lower charge states considerable deviation from the neutral molecule bond angle has been found. These results suggest that production of higher charge states is favorable for the fulfillment of a pure Coulombic dissociation scheme.

Single-wall carbon nanotubes (SWNTs) were synthesized in high yield by laser vaporization of a Rh/Pd-graphite composite rod at 1200 °C. Lattice constants of the bundle were estimated from transmission-electron-microscope images and were found to be distributed between 1.0 and 1.5 nm. Nine Raman peaks originating from the breathing modes were observed at 204, 215, 229, 247, 262, 272, 287, 303 and 328 cm-1. These frequencies and lattice constants sharply indicate the presence of the SWNTs indexed from (5,5) to (8,8) which are thinner than the SWNTs obtained using Ni/Co catalyst.

Dependences of the photoinduced radical-anion formation of solute-solvent charge-transfer complexes upon the exciting light intensity have been studied spectroscopically in ether-isopentane glass as well as in 2-methyltetrahydrofuran (MTHF) glass at 77 K. Biophotonic ionic dissociations have been found for the following complexes: TCNB(tetracyanobenzene)-ether, PMDA(pyromellitic dianhydride)-ether, TCPA(tetrachlorophthalic anhydride)-ether and TCPA-MTHF.

Using nonresonant microwave absorption in low magnetic field (so called LFS) combined with conventional ESR it is shown that degradation of the superconducting (SC) state of K X C 60 upon exposure to air is a surprisingly slow (e.g. compared to n-type doped conducting polymers) and partially reversible process. The annealing at 100–130°C in high vacuum of air exposed samples restores both LFS and ESR typical for the SC state, suggesting the formation of some unstable (K X C 60 O 2 ) complex at a first stages of oxidation. At longer exposure times superconducting LFS can not be recovered meaning irreversible chemical bonding of 0 to C 60 .

The Raman scattering at 1.16 eV laser excitation has been studied in ferromagnetic TDAE-C60 and compared to that in paramagnetic TDAE-C70. The shift of Hg and Ag modes in TDAE-C60 indicates transfer of one electron to C60 while the broadening of Hg modes is quite similar to metallic K3C60 meaning significant electron-phonon coupling of this Jahn - Teller vibrations. In TDAE-C70 the lines are narrow sugesting suppresed electron - phonon interaction and hence smaller polaronic effects. Below Tc of magnetic ordering the two-magnon excitations are not seen clearly however the low energy part of spectra shows somewhat increased intensity. Upon air-exposure of TDAE-C60 all Hg and Ag Raman modes disappear while a new band appears at 1848 cm−1.

To see the bundle effects on the electronic and the vibrational properties of single-wall carbon nanotubes (SWNTs), we have measured the resonance Raman scattering of isolated SWNTs and thick bundles. For the measurements of the isolated SWNTs, we used an evacuated sample after bromine doping. A broad and asymmetric tangential mode band, which is a sign of the resonance of the metallic SWNTs and can be fitted by a Fano line shape, is not observed in the isolated SWNTs. This suggests the inter-tube interactions play an important role to the Fano interference. On the other hand, the purified sample shows very thick acquired bundles. We observed 4% higher breathing mode frequencies than in the pristine sample. Further, in the case of multi-wall nanotubes, we observed 5% higher breathing mode frequencies than the SWNTs. These results can be explained by the interlayer interactions.

High‐yield fullerene‐peapods were synthesized by using diameter selected nanotubes. Filling factors of C60 and C70 were estimated from X‐ray diffraction analysis. The best filling is 100 % for C70‐peapods. Peapods were transformed to double‐wall nanotubes simply by heating in vacuum. Drastic spectral change in radial breathing modes and tangential modes were observed with an intensity drop in the conversion process. Limited number of radial breathing mode peaks originated from inner nanotubes was observed in resonance Raman spectra, which is consistent with a tight binding calculation of electronic band structure for thin nanotubes.

Charge transfer complexes of polycyclic aromatic hydrocarbons with alkali metal are known to adsorb hydrogen chemisorptively. We investigate hydrogen uptake effects on the properties of metallic K 3 C 60 by means of ESR and superconductivity measurements. The introduction of hydrogen induces a disproportionation reaction, resulting in the generation of K 6 C 60 domains which have interstitial sites available for the accomodation of dissociated hydrogen atoms. The annealing process makes the hydrogenated K 3 C 60 homogeneous where small amounts of hydrogen are stabilized as impurities. Superconductivity is not influenced by hydrogen uptake.

We have investigated polarized absorption and Raman spectra of aligned single-walled carbon nanotubes in polymer. The optical transitions in nanotubes strongly depend on the angle θ between the polarization of incident light and nanotube axis: the absorbance measured at the peak energy shows a maximum at θ=0°, and they are suppressed at θ=90°. Raman spectra also show strong polarization dependence, which is mainly determined by the dependence of oscillator strength of optical transition in nanotube.

Electronic structure of single‐wall carbon nanotubes was investigated by photoemission spectroscopy. Oscillations in electronic density of states due to one‐dimensional van Hove singularities were clearly observed near the Fermi level, which can be well reproduced by simple tight‐binding calculation with assumptions a broadening and an energy shift probably due to a charge transfer from the metal substrate. Furthermore, in the vicinity of the Fermi level, two kinds of typical power‐law dependences were observed that can be regarded as evidence of Tomonaga‐Luttinger liquid states. Both exponents show very similar values 0.46 and 0.48 good agreement with theoretical prediction. Results on fullerene peapod system are also discussed.

Raman experiments are reported for seven samples of SWCNT with different diameters. The characteristic oscillations in the first and second moment of the radial breathing mode are used to determine the mean diameter of the tubes. These results are compared to results obtained by optical absorption and x-ray experiments. Oscillating behavior was also observed for frequencies of other modes such as the D and D* mode and for the intensities of the RBM, the D band, the G band and the D* band. Oscillations could be ascribed to the resonance of tubes with different diameters which are present in one sample.

Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni-Co-graphite composite targets at 1200 °C under flowing argon. The effects of the temperature gradient near the target and the gas flow rate on the diameter distribution of SWNTs were studied in order to understand their growth dynamics. The diameter distribution of the SWNTs, analyzed by Raman spectroscopy, was dependent on the gas flow rate when there was a temperature gradient around the target. Time resolved scattering images from the ablated species at different flow rates indicated that velocities of backward moving species increased with increasing flow rate. These findings are used to estimate the time required for nucleation and the growth of SWNTs.

We have used scanning tunneling microscope (STM), operated in ambient conditions, to investigate the atomic structure of single walled-carbon nanotubes (SWNT). The microscopic scale images show tubes condensed in ropes as well as tubes which are separated from each other. For a single-wall nanotube rope, the outer portion is composed of highly oriented nanotubes with nearly uniform diameter and chirality. On separated nanotubes, atomically resolved images show variable chirality ranges between 0–30°, and variable diameter (1–3 nm ), with no one type dominant. From STM and scanning tunneling spectroscopy (STS) measurements we confirmed the correlation between the structural parameters and the electronic properties, namely the tuning from metallic to semiconducting. We also observed a rectifying behavior correlated with the chiral angle of 25°, an important observation for nano-devices application.

A novel passively mode-locked fiber laser is demonstrated using saturable absorber based on single-walled carbon nanotubes. This is the first demonstration of an optical pulsed laser based on carbon nanotube technology.

The structures of carbonaceous deposits obtained through laser ablations using targets composed of C, Ni, and Co under various Ar gas pressures were studied. The pressure dependence of the target's...

By means of low magnetic-field micowave absorption (Low-Field Signal) and conventional ESR, we have studied the evolution of superconductivity in bulk KxC60 dependent on the variation of K- doping temperature and time. The first LFS as an occurrence of superconductivity is observed in a doping time as short as td = 0.5 h with a discrete Tc ∼ 19 K, and the volume of the superconducting phase increases on further dopings, while Tc changes slightly. The sample in a superconducting state exhibits strong ESR absorptions, which indicates the presence of a non-superconducting metallic phase coexisting with a superconducting phase in inhomogeneously doped KxC60. These phases are closely correlated and disappear at the same time by overdoping.