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X-ray absorption spectra (XAS) of the lowest excited singlet, triplet, and ground states (S 1 , T 1 , S 0 -XAS) of benzoic acid and methyl benzoate in the O 1s region were calculated. Resonant core transition to a hole at the highest occupied molecular orbital (HOMO) created by valence excitation was predicted about 3 eV below the lowest peak of S 0 -XAS but with very weak intensity. A strong peak of the T 1 -XAS well separated from S 0 -XAS peaks is found for both molecules so that identification of the core-excitations from the T 1 and selective excitation of the T 1 become possible. Bond dynamics of oxygen-containing bonds in the potential energy surface of valence and core doubly excited states are estimated by using molecular dynamics simulation. Enhancement in known state-selective dissociation and new type of state selectiteve dissociation are predicted for the core excitations from valence excited state.

Dissociation of free acetonitrile-d3 molecule, CD3CN induced by core level excitation was studied near the nitrogen K-edge by time-of-flight fragment mass spectroscopy. A variety of atomic and molecular fragment cations such as D+, CDn+, C2Dn+, and CDnCN+ were detected using the effusive CD3CN beam. Photoelectron–photoion–photoion coincidence technique was applied to analyse the dissociation mechanisms and dynamics of doubly charged CD3CN2+ following the N(1s–π*) excitation. The charge separation mechanisms of core-excited CD3CN were discussed in connection with Auger final state distributions.

A compact varied-line-spacing plane grating monochromator has been constructed at the bending magnet beamline BL6 of the HiSOR facility in Hiroshima University. The monochromator covers the energy range of 200–1200 eV with two gratings. The performance of the monochromator is evaluated from total-ion yield spectra of Ar, N2, and Ne. The obtained resolving powers ( E / Δ E ) are ∼ 5000 (Ar L-edge), ∼ 6400 (N K-edge), and ∼ 4600 (Ne K-edge). High mass resolution electron–ion–ion coincidence apparatus is mounted at an end station of the beamline to investigate ionic dissociation processes of core-excited complex organic molecules. Multiple fragmentation processes from core-excited ammonia (NH3) and ionic dissociation processes from core-excited benzyl alcohol (C6H5CH2OH) are also discussed.

Total photoabsorption spectra of CF 3 COCH 3 were measured in the C, F and O K-shell regions and the peak assignments were tentatively given. The K-shell electrons of C, F and O atoms were selectively excited into the π * orbital. The kinetic energy (KE) distribution of CF 3 + formed through the π * states gave the maxima at KE = 0 and 0.43 eV. The yield of CF 3 + with KE = 0 eV increased from 10 to 50% by changing the excitation sites from F 1s to O 1s. This finding was reasonably understood by considering that intramolecular energy flows from the initially excited K-shell electron to vibrational modes of CF 3 group. The KE distribution of CH 3 + showed a mirror image of that for CF 3 + .

Auger electron spectra were studied by scanning the photon energy near the L 3 threshold of krypton. Two resonant transitions were observed in the photon energy region 1673–1678 eV for the first time. They were identified to be the resonant 3d -2 5s and 3d -2 4d states originating in the 2p 3/2-1 5s and 2p 3/2-1 4d excitations, respectively.

Normal Auger electron spectra from Kr2p hole states, L 23 M 45 M 45 and L 23 M 23 M 45, have been measured using monochromatized synchrotron radiation and a high resolution electron spectrometer. Measured spectra were reproduced with a fitting calculation, where Voigt functions including an instrumental resolution and natural lifetime widths of related core hole states were used. At most final states estimated energies for spectral peaks agree with those by electron and ion beam techniques. Relative intensities for some peaks are appreciably different from the previous results.

Resonant Auger spectra of H2O are recorded with unprecedented resolution, for excitation energies tuned across the O 1s→2b2 resonance. Electron emission spectra for decay to the 1b2-1 final state show a partially resolved vibrational envelope whose overall appearance is photon energy dependent. Comparison with ab initio calculations indicates that the two-dimensional nuclear motion of the Auger final state can be controlled by sampling different portions of the potential curve and changing the nuclear motion in the core-excited state.

A new soft X-ray beamline has been constructed at the Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University. This beamline has a unique mechanism of an exchange system for a monochromator crystal. A double crystal monochromator of a Golovchenko-type is equipped with a crystal bank. The beamline delivers photons with energies from 800 to 5000 eV. Users can obtain the effective X-ray absorption fine structure spectra for Si, P, S, Cl, Ar and K K-edge on this beamline.

We report the first results from a spherical grating monochromator for the linear undulator beamline ( hν =26–300 eV) at a compact 700 MeV electron-storage ring (HiSOR) at Hiroshima University. The Rydberg series of Ne ( hν ∼48 eV) up to n =20 and the double excitation spectrum of He ( hν ∼65 eV) up to n =20+have been observed. The maximum energy resolving power ( E /Δ E ) at hν ∼65 eV is estimated to be >16,000 with the photon flux >10 10 photons/s.

Angle-resolved energetic-ion yield spectra have been observed in the O 1s excitation region of H2O and D2O with the incident photon-energy resolution better than 14 000 . Vibrational structures appear in most of the Rydberg members and are ascribed to the bending vibrations. The assignments of the electronic states are established on the basis of the angular distribution data for the energetic ions.

The quantitative photofragment fluorescence spectroscopy, using the synchrotron radiation as an exciting light source, was applied to study the Rydberg and high-lying valence states of ClCN observed as congested structures in the vacuum ultraviolet region. The absolute cross-section and quantum yield for the CN(B 2 R a ‐X 2 R a ) emission produced in the photodissociation process of ClCN were determined in the wavelength range 105‐145 nm (69 000‐95 200 cm ˇ1 ). The quantum yield for the CN(B 2 R a ) production takes a maximum value of0.13 at84 000 cm ˇ1 . The emission of CN(B 2 R a ‐X 2 R a ) transition was found to be partially polarized with respect to the direction of the electric vector of the excitation synchrotron radiation. The polarization anisotropy of this emission, which depends on the symmetry of absorption transitions into the photodissociative states of ClCN was measured as a function of exciting wavelength. The relative cross-section for the production of CN(A 2 Pi‐X 2 R a ) emission was also determined. Based on the measured photochemical properties of the high-energy electronic states, the observed bands of the Rydberg and intravalence

Absolute photoabsorption and fluorescence cross sections of gaseous SiCl4 have been measured in the energy region 6.2–31 eV using synchrotron radiation as the light source. Higher order light from the 1-m Seya monochromator was suppressed by use of an Ar gas filter in the energy range 11.3–15.5 eV (110–80 nm) and a LiF window at hν

We have measured high-resolution total- and partial-ion yield spectra of NH 3 . The obtained total-ion yield spectrum exhibits more detailed structure than the absorption spectrum reported previously. The observed structure at the N 1s → 3sa 1 resonance is assigned as the vibrational progressions of symmetric stretching ν 1 and bending ν 2 mode. A dissociation channel mediated by the vibrational motion in the core-excited state of NH 3 was observed. We focus on this vibrational structure and the formation process of NH 3 2 + , which remarkably depends on the vibrational state (and/or energy) in the core-excited state.

Molecular and dissociative photoionization branching ratios and photofragment appearance potentials of BrCN have been determined using dipole (e, e + ion) spectroscopy at equivalent photon energies from the first ionization threshold up to 160 eV. Absolute partial photoionization oscillator strengths (cross sections) for the molecular and dissociative photoions have been obtained from the triple product of the photofragment branching ratio, the photoionization efficiency, and the previously reported absolute photoabsorption oscillator strength [Olney et al., Chem. Phys. 201 (1995) 505]. Information on the Coulomb explosion decay channels of doubly and triply charged molecular ions has been obtained from photoion-photoion coincidence (PIPICO) spectroscopy using synchrotron radiation as a light source in the 40–130 eV photon energy range. While stable doubly charged ions are formed in both the valence and the Br 3d regions no stable triply charged ions are observed. However, the PIPICO measurements detect time correlated singly and doubly charged fragment species resulting from Coulomb explosion of triply charged ions which are first formed at the Br 3d excitation threshold and throughout the ionization continuum by triple autoionization and double Auger type processes. The experimental results provide information on the dipole induced breakdown pathways resulting from valence shell and Br 3d ionization processes in BrCN.

The threshold photoelectron spectrum of CF4 up to 60.5 eV has been recorded using synchrotron radiation and a penetrating-field electron spectrometer of high resolution. Our results confirm the broad spectral features of the X 2T1, A2T2 and B 2E state bands of CF4+ reported previously with He I PES. The influence of autoionizing super-excited states of CF4 has been observed as an extension of the high-energy tail of the B 2E state, as a structured band in the energy region between the B 2E and C 2T2 states, and as additional vibrational structure extending the D 2A1 state band. Improved spectra of the C 2T2 and D 2A1 states have been obtained as a consequence of the high resolution of this study. The overall electronic state band profiles observed here up to about 26eV agree with a recently published low-resolution threshold photoelectron spectrum of CF4 [Creasey et al., Chem. Phys., 174 (1993) 441]. Between 26 and 60.5 eV a continuum-like background was observed with some broad-band features superimposed on it. One broad peak, centered on 40.3 eV, is tentatively assigned to the formation of the Ẽ 2T2 and F 2A1 states of CF4+, but the formation of the double-charged ion, CF42+, may also be involved.

We have designed and constructed the apparatus for the angular distribution measurements of photoejected electrons and ions from free molecules, as a part of the endstation of the c -branch of the beamline BL27SU, a soft X-ray photochemistry beamline at SPring-8. The experimental procedures are described in combination with the use of a capability to switch the horizontal and vertical directions of the linear polarization of the light produced by the figure-8 undulator. As a typical example of the experimental results, we present angle-resolved energetic ion yield spectra in the O 1s excitation region of CO 2 .

Total electron–ion–ion coincidence measurements on core excited organic molecules have been carried out with high mass resolution by using multimode (reflectron/linear) time-of-flight mass analyzer. From the ion correlation spectra of core excited CH3OH and CD3OH, the reaction pathway to form H3+ (D3+) is identified as the elimination of three H (D) atoms from the methyl group, not as the inter-group (–CH3 and –OH) interactions. In a PEPIPICO spectrum of acetylacetone (CH3COCH2COCH3) measured by using a reflectron TOF, correlations between ions up to mass number 70 with one-mass resolution was recorded.

The location and identity of low-lying electronic states of jet-cooled isoquinoline have been investigated by multiphoton ionization photoelectron spectroscopy, involving one-color well as two-color ionization schemes. The results provide evidence for the presence of an nπ* triplet state lying between the lowest excited singlet state of nπ* character and the lowest triplet state of /gp/gp* character.

The absorption spectrum of solid Ne measured in the 800-1300 eV region is presented. Two sharp peaks near the K -edge around 865 eV which correspond to the 1 s →3 p and 1 s →4 p transitions in gaseous Ne are attributed to the excitonic transitions. Above the ionization energy of 1 s electron in gaseous Ne, many structures are observed in solid Ne.

We study the electronic structure and chemical bonding of the ${\text{SO}}_{2}$ molecule adsorbed on Ni(100) surface using x-ray emission spectroscopy at the $\text{O}\text{ }1s$ absorption edge. Elemental and symmetry specificities of the method enable us to directly probe surface chemical bonding formed by strong hybridization of $\text{O}\text{ }2p$ with $\text{Ni}\text{ }3d$ orbital. Contrary to the expected $\ensuremath{\pi}$ bonding due to strong $\ensuremath{\pi}$ acceptor character of the ${\text{SO}}_{2}$ molecule, we find electronic structures with both $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ characters just below the Ni Fermi level. The details of this complicated surface chemical bonding are discussed using a calculation based on density-functional theory.

Photodissociative excitation processes of gaseous HNCO are studied in the wavelength region 107–180 nm using synchrotron radiation as a light source. Fluorescence excitation spectra of the photofragments, NH(c 1 Π, A 3 Π) and NCO(A 2 Σ), are measured under near collision-free conditions. The quantum yields for formation of these excited radicals are also determined.

Soft X-ray absorption spectra of the lowest excited triplet states of several organic molecules (quinones, benzaldehydes, and other carbonyls) and potential curves of valence- and core- doubly excited states are calculated for the O 1s region.

Synchrotron radiation emitted from the UVSOR storage ring is monochromated by a grazing-incidence monochromator and introduced coaxially with the second harmonic of a mode-locked Ti:sapphire laser. Sample gases, N2 and N2O, are photoionized into vibronically ground N2 + with the fundamental light of the undulator radiation at 18.0 and 18.6 eV, respectively. Laser-induced fluorescence (LIF) excitation spectra of N2 + from N2 and N2O are measured in the laser wavelength region of the (B 2Σ u +, v′ = 0) ← (X 2Σg +, v′′ = 0) transition at 389–392 nm. The LIF excitation spectra of N2 + exhibit two maxima due to the P and R branches in which rotational bands are heavily overlapped. The rotational temperature is determined by simulating an LIF excitation spectrum by using the theoretical intensity distribution of rotation bands convoluted with the spectral width of the laser.

Vibrationally resolved spectra have been obtained for the lowest-lying cationic states X (2)B(1), A (2)A(1), and B (2)B(2) of the water molecule reached after participator resonant Auger decay of core-excited states. The angular distribution has been measured of the first four vibrational components of the X state in the photon energy regions including the O 1s-->4a(1) and the O 1s-->2b(2) core excitations, and for different portions of the vibrational envelope of the B state in the photon energy region including the O 1s-->2b(2) core excitation. For the X state, a large relative spread in beta values of the different vibrational components is observed across both resonances. For the B state, a very different trend is observed for the high binding energy side and the low binding energy side of the related spectral feature as a function of photon energy. A theoretical method based on the scattering K matrix has been used to calculate both the photoabsorption spectrum and the beta values, by taking both interference between direct and resonant photoemission and vibrational/lifetime interference into account. The numerical results show qualitative agreement with the trends detected in the experimental values and explain the conspicuous variations of the beta values primarily in terms of coupling between direct and resonant photoemission by interaction terms of different sign for different final vibrational states.

Twin helical undulators and five kicker magnets have been installed in the 5 m straight section of SPring‐8 BL25SU to provide helicity switched circularly polarized radiation in soft X‐rays. Helicity of circular polarization is changed by means of electron beam orbit bumps. We successfully increased frequency up to 10 Hz without disturbing the stability of the electron beam orbit.

The Cu L2,3‐edge x‐ray absorption fine structures (XAFS) of a series of Cu samples have been recorded at the BL1A beamline of UVSOR using both electron yield and x‐ray fluorescence yield techniques. XAFS measurements were simultaneously recorded in three modes: total electron yield (TEY) with specimen current, total electron yield with a channeltron electron multiplier and x‐ray fluorescence yield (FLY) with an Ar/CH4 gas proportional counter. While both TEY measurements produce essentially identical spectra, a comparison between TEY and FLY results shows a drastic difference in the sensitivity of the techniques towards sampling depth. These results and their implications are discussed.

The vibrational structure of the $\mathrm{O} {1s}^{\ensuremath{-}1}{2b}_{2}$ core-excited state of ${\mathrm{H}}_{2}\mathrm{O}$ is observed and ascribed to the mixture of symmetric stretching and bending motions with ${a}_{1}$ symmetry. The formation of ${\mathrm{H}}_{2}^{+}$ is found to increase linearly with an increase in energy stored in the nuclear motion of the $\mathrm{O} {1s}^{\ensuremath{-}1}{2b}_{2}$ state, demonstrating that this dissociation channel is mediated by the nuclear motion in the core-excited state. The reaction pathway to the ${\mathrm{H}}_{2}^{+}$ formation along the Auger final state of ${\mathrm{H}}_{2}{\mathrm{O}}^{+},$ mediated by the nuclear motion before the Auger decay, is discussed with the help of ab initio potential surfaces of the Auger final states.

X-ray excited optical luminescence yield spectra of single crystals of pure NaBr and Cu-activated NaBr are reported. X-rays are scanned at the energy regions of K edges of Br and Na. The yield spectra for the intrinsic luminescence emission band of NaBr at 4.5 eV for both samples and those for the Cu impurity luminescence band at 3.4 eV are compared. The results show that in the NaBr:Cu, both positive and negative edge jumps are observed depending on the monitored emission band. The yield spectra are reproduced with the calculation following our recent phenomenological theory.

Combining a photoelectron spectroscopic technique with a (1+1) resonant ionization method, we have investigated photoelectron spectra by ionizing naphthalene through single vibronic levels of the S1 state up to an internal energy (Evib) of about 2500 cm−1 as well as through some vibronic levels of the S2 origin region. The photoelectron spectra thus obtained have been found to show many bands which are interpreted as the vibrational structure of the naphthalene cation. The present photoelectron results also support the available spectroscopic evidence that intramolecular vibrational redistribution occurs at the energy levels higher than 2200 cm−1 above the S1 origin. Intramolecular electronic relaxation from the S2 to the S1 state has been found to be faster than ionization under the present laser irradiation conditions, suggesting that the relaxation rate is larger than an order of 1011 s−1.

The fluorescence excitation spectrum of the first singlet transition of aniline in a supersonic free jet has been measured. Vibronic transitions involving the inversion vibration of the NH 2 group in the excited state have been observed. The double minimum potential function in the excited state has been determined from the observed vibrational levels.

In vacuum ultraviolet photolyses of CCl4 and CBrCl3 a diffuse emission band was observed in the region of 410–750 nm by Ar i resonance and H Lyman‐α line irradiation. The band was attributed to a CCl2(A 1B1 → X 1A1) transition from the measurements of the appearance energies of the emitters produced from photodissociative excitation of both CCl4 and CBrCl3 using synchrotron radiation. The fluorescence decay of the CCl2(A → X) transition showed a superposition of two lifetime components of 2.17±0.26 and 4.0±0.12 μs at pressures from 10 to 140 mTorr. The pressure dependence of the amplitudes for the two lifetimes suggests the occurrence of collision‐induced intersystem crossing between 1B1 and 3B1 states of CCl2 radicals. The absorption cross section of CBrCl3 was measured for the first time in the 106–200 nm wavelength region and tentative assignments of Rydberg transitions are presented.

A detailed study of the vacuum ultraviolet fluorescence excitation spectrum of I2 in the region 110–210 nm is reported. Both absorption and fluorescence excitation spectra were recorded simultaneously using continuously tunable synchrotron radiation. At long wavelengths (176–210 nm) the fluorescence excitation spectrum is dominated by the D(0+u) ion‐pair state. Perturbations between the D(0+u) state and isoenergetic levels of the c6 Rydberg state lead to pronounced resonances (dips) in the fluorescence excitation spectrum. Weaker absorption to the F(0+u) and F’(0+u) ion‐pair states is identified at 170 and 150 nm, respectively. Below 149 nm electronically excited iodine atoms (I 6s 4P5/2 and I 6s 2P3/2) are formed by predissociation of high‐lying Rydberg and ion‐pair states.

The photoabsorption cross section and fluorescence excitation spectra of C 2 Cl 6 have been investigated in the 105–200 nm region using synchrotron radiation as a light source. The absorption bands observed are assigned as the Rydberg excitations. The fluorescence yield starts at about 160 nm and increases to Φ=0.18 at 111.5 nm. The emitting species is CCl 2 (A 1 B 1 →X 1 A 1 ); its radiative lifetime was determined to be 1.83±0.02 μs.

Absorption and fluorescence excitation spectra of I 2 have been recorded in the region 1100–2100 A using synchrotron radiation. The strongest fluorescence is excited in the region 1730–2000 A and is associated with the D(0 u + ) ion-pair state: fluorescence in the region 1320–1500 A is assigned in part to excited atoms formed by predissociation of Rydberg states.

Photoabsorption cross sections of thiirane and thietane vapors have been studied in the 110–240 nm region using synchrotron radiation. A number of peaks from thiirane and thietane are arranged into four and five Rydberg series, respectively, converging to the first ionization potential. Many Rydberg peaks from both molecules are observed to possess vibronic structures. The vibrational progressions from thiirane are assigned to the CH2 wagging (ν4) and CS symmetry stretching (ν5) modes. For thietane, the CH2 wagging (ν5) and CS symmetry stretching (ν7) modes of the excited states are found to be active. Molecular geometries and vibrational frequencies for the excited states are discussed on the basis of ab initio calculations.

Combining a photoelectron spectroscopic technique with a (1+1) resonant ionization method, we have investigated intramolecular decay processes of benzene in its S 1 state under collision‐free conditions. Photoelectron spectra were obtained by selective excitation of benzene with a pulsed UV laser at several single vibronic levels of the S 1 state up to an internal energy (ΔE) of 5000 cm− 1. These spectra strongly suggest that the excitation of benzene at the vibronic bands above the onset of the ‘‘channel three’’ is followed by intramolecular vibrational redistribution within the S 1 state. It is concluded that there are no decay channels faster than this redistribution process up to ΔE=5000 cm− 1 at the first decay stage. The results of the integrated multiphoton ionization intensity distribution over the vibronic bands, as well as the internal‐energy dependent spectral changes observed in the photoelectron spectra, also strongly suggest that the channel three is initiated by the redistributed vibrational modes, which lead to a fast internal conversion leads to the ground electronic state.