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We report on the selective-area growth and characterization of wurtzite (WZ) InP/AlGaP core–multishell nanowires. Quantum well (QW) structures were fabricated in AlGaP multishells by changing the alloy composition. Transmission electron microscopy revealed that the AlGaP multishells were grown with a WZ structure on the side of the WZ InP core. The lattice constants of the WZ InP core and WZ AlGaP shell were determined by X-ray diffraction. Cathodoluminescence studies showed that the WZ AlGaP QW with an Al composition of 20% exhibited green emissions at 2.37 eV. These results open the possibility of fabricating green light-emitting diodes using WZ AlGaP-based materials.

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

High resolution Cu L 3,2 -edge XANES have been obtained for Cu metal and a series of Cu-Au alloys (CU 3 Au, CuAu and CuAu 3 ). It was found that the Cu L 3 -edge XANES for all the samples under investigation exhibit the characteristic three-peak resonances predicted by theory. The CU L 3 -edge XANES shows some interesting systematics which can be correlated to charge redistribution in Cu-Au alloys.

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

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.

We grew AlInP on two types of GaN substrate in order to transfer the wurtzite (WZ) structure to grown layers. An AlInP epitaxial layer grown on GaN with high-density stacking faults was obtained. X-ray diffraction and Raman scattering analyses indicate that the dominant crystal structure of the AlInP layer grown on GaN was WZ. Cathode luminescence measurements at 35 K revealed strong green emissions from the WZ AlInP layer, suggesting an energy band gap change from indirect to direct. These results demonstrate the potential of WZ AlInP as a new candidate for high-efficiency green emission material.

Fragmentation of doubly charged ethanol clusters [(C(2)H(5)OH)(n)] following the O 1s ionization has been investigated by means of the photoelectron-photoion-photoion coincidence (PEPIPICO) method. The dominant fission channel of (C(2)H(5)OH)(n)(2+) was the formation of protonated cluster ion pairs [H(C(2)H(5)OH)(l)(+)/H(C(2)H(5)OH)(m)(+)]. The fragmentation mechanisms of these ion pairs were discussed based on the analysis of the PEPIPICO contour shape. It was clarified that the prominent fragmentation channel was a secondary decay mechanism, where neutral evaporation occurs after charge separation. On the other hand, the formation of small fragment ions was suppressed, excluding the formation of certain specific fragments (H(3)O(+), C(2)H(5)(+)/COH(+), and C(2)H(4)OH(+)). The formation of small fragment ions was suppressed due to the cooling effect caused by the neutral evaporation and the decrease in the electrostatic repulsive force caused by charge separation.

Photoabsorption and fluorescence excitation spectra of CHBr2Cl and CHBrCl2 trihalomethanes were measured in the 106–200 nm region using synchrotron radiation as a light source. Main photoabsorption bands observed are assigned as the Rydberg transitions of the outer shell orbitals. In the photoexcitation of CHBr2Cl a diffuse emission band of CHCl(A 1A‘→X 1A’) was observed in the 500–800 nm region. The radiative lifetime of the CHCl(A 1A‘) state was first determined to be 7.01±0.25 μs. In the photolysis of CHBrCl2 at 121.6 nm, the formation of CHCl(A 1A‘) and CCl2(A 1B1) radicals were observed. The fluorescence thresholds for CHBr2Cl and CHBrCl2 start at 162 and 159 nm with the maximum yields of 5% and 11% at 122 and 119 nm, respectively.

A study of the excitation energy dependence of resonant X-ray emission spectra across the O1s absorption edge in combination with X-ray absorption spectroscopy and density functional theory reveals the site-specific valence electronic structure of liquid acetic acid under ambient conditions.

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 direct absorption spectrum of benzene in a free jet has been measured in the 130–260 nm region (S1, S2, and S3 states, Rydberg series, and the first ionization limit) using synchrotron radiation as a light source. The absolute molar extinction coefficients (e) of benzene in jets have been determined by scaling measured free‐jet values to the known value in the vapor phase for a broadband at 200.1 nm in the S2 state. The vibrational temperature for ν16 mode was estimated to be 185 K. The maximum value of e of the S1 absorption system was found to be 1400 l mol−1 cm−1 (spectral bandwidth=0.065 nm). A shoulder observed at 205.45 nm in the S2 absorption system is assigned to the S2 origin, induced by pseudo‐Jahn–Teller distortion.

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.

The direct absorption spectra of benzene in jets are measured in the wavelength region of the S 2 and S 3 system, using synchrotron radiation (SR) as a light source. Two broad absorption maxima are found at 208 and 185 nm and assigned, respectively, to the S 2 and the S 3 absorption system of benzene clusters. Large stability in the S 2 and S 3 states upon cluster formation, by at least 6 kcal/mol, is concluded from the observed red-shifts with respect to the monomer bands.

Hydrogen bonding in methanol clusters has been investigated by using inner-shell photoabsorption spectroscopy and density functional theory (DFT) calculations in the carbon and oxygen K-edge regions. The partial-ion-yield (PIY) curves of H(CH(3)OH)(n)(+) were measured as the soft x-ray absorption spectra of methanol clusters. The first resonance peak in the PIY curves, which is assigned to the sigma*(O-H) resonance transition, exhibits a 1.20 eV blueshift relative to the total-ion-yield (TIY) curves of molecular methanol in the oxygen K-edge region, while it exhibits a shift of only 0.25 eV in the carbon K-edge region. Decreased intensities of the transitions to higher Rydberg orbitals were observed in the PIY curves of the clusters. The drastic change in the sigma*(O-H) resonance transition is interpreted by the change in the character of the sigma*(O-H) molecular orbital at the H-donating OH site due to the hydrogen-bonding interaction.

Photoabsorption and fluorescence excitation spectra of CHFCl2 and CHFBr2 were measured in the wavelength region 106–200 nm using synchrotron radiation as a light source. The Rydberg excitations of the outer shell orbitals are discussed. The He(i) photoelectron spectrum of CHFBr2 was first measured. Diffuse emission band of CHF(A 1A‘→X 1A’) was observed in the 350–700 nm region, in which the 2n0 (n=0–4) vibrational progression and 201 transition were identified. The CClF(A 1A‘) radical was produced together with CHF(A 1A‘) in the photodecomposition of CHFCl2. The radiative lifetimes of the A 1A‘ states of CHF and CClF were determined to be 2.57±0.16 μs and 644±15 ns, respectively. In the photolysis of CHFCl2 fluorescence starts at 155 nm and shows a maximum quantum yield Φ=0.22 at 107.5 nm, while the CHFBr2 excitation gives a maximum of Φ=0.016 at 117.5 nm.

The photoabsorption cross sections and fluorescence excitation spectra of group IIb dimethylmetals were measured using synchrotron radiation at 106–270 nm. The observed absorption bands were accounted for in terms of Rydberg transitions. The fluorescence spectra of MCH3 (A 2E→X 2A1) transitions were observed and the radiative lifetimes determined were 47±2 and 62±2 ns for M=Zn and Cd, respectively. The excited M(np 3P01) atoms were detected in the photolyses of dimethylcadmium and dimethylmercury, but not in dimethylzinc. The formations of the electronically excited MCH3 (A 2E) and M(np 3P01) states are characteristic of the Rydberg excitations of the C–H in methyl and M–C bonding electrons, respectively.

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.

Time-of-flight mass spectra have been measured for inner-shell ionization of ethanol molecules, its clusters, and methanol clusters at the oxygen K-edge regions. Only in the case of the ethanol clusters, a fairly intense signal corresponding to H 3 O + has been observed. The measurements for ethanol- d 1 (C 2 H 5 OD) suggest that at least one H atom in the H 3 O + ion originates from the C 2 H 5 group of neighbouring ethanol. It is proposed that in addition to the O–H⋯OH type hydrogen bonding in the ethanol clusters, the H in the C 2 H 5 group and OH interact with each other.

Ionic fragmentation of core-excited α-alanine in gas phase was observed. The most dominant ionic species is COOH+ for all core-ionizations at C 1s, N 1s, and O 1s. An increase in COO+ and a decrease in COOH+, which were observed as core-hole atom selectivity for the O 1s ionization, are explained by the enhancement of O–H bond scission. Further state-selective O–H bond scission, observed at the O 1s second peak, is attributed to the OOH1s → 3s/σ* transition.

Dissociation of free methyl-formate (MF), HC(O)OCH3, and its clusters (MF)n, (HC(O)OCH3)n, induced by core-level excitation was studied near the oxygen K edge by time-of-flight fragment-mass spectroscopy. Besides the protonated clusters, (MF)nH+ with n < or = 15, we identified the production for another series of (MF)mCH3OH2+ with m < or = 14 as well as methyl-oxonium ion, CH3OH2+, characteristic of hydrogen transfer reactions in the cationic clusters. Here; specifically labeled methyl-formate-d (MFD), DC(O)OCH3 was also used to examine the core-excited dissociation mechanisms. Deuterium-labeled experiments indicated that MFD+ with low internal energies, partially generated after the core excitation, produces CH3OD+ via a site-specific deuterium transfer from the alpha carbonyl in the molecular cation and that CH3OD2+ can be formed via the successive transfer of another deuterium from the neighbor molecule in the clusters. The deuteron (proton) transfer was also found to take place preferentially from the alpha carbonyl of the neighbor molecule for the production of deuteronated (MFD)nD+, (protonated (MF)nH+), clusters. The minimal energy requirement paths were examined for dimer (MF)2+ cation to support the present dissociation mechanisms of core-excited (MF)n clusters using ab initio molecular-orbital calculations.

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.

High‐resolution neutron powder diffraction measurements with λ=1.8232 A and collimation of 6’‐20’‐6’ on Nd2Fe17Nx with x=0, 2.85, and 2.91 were carried out at room temperature. Structural parameters and magnetic moments were determined by the Rietveld profile‐fitting calculation. The magnetic moments of iron atoms increased with increasing nitrogen concentration; e.g., the magnetic moments of iron located at 6c, 9d, 18f, and 18h sites increase from less than 0.7μB in the x=0 sample to about 2.1μB in the x=2.91 sample. It is noticed that a local atomic group composed of two Fe(1) atoms at the 6c site plus six Fe(3) atoms at the 18f site keeps its shape against the nitrogen uptake.

Pronounced polarization dependence of the X-ray emission spectrum, which reflects the symmetry of the initial valence molecular orbital, was observed for acetic acid in acetonitrile solution under ambient conditions.

Occupied valence electronic structures in the neutral and the anionic forms of aqueous acetic acid and their pH dependence under ambient condition are identified for the first time exploiting the site-selectivity of resonant X-ray emission spectroscopy (XES) in combination with calculation based on density functional theory (DFT).

Both anisotropic ablation and thin film formation of polytetrafluoroethylene (PTFE) were successfully demonstrated using synchrotron radiation (SR) irradiation of PTFE, that is, the SR ablation process. Anisotropic ablation by the SR irradiation was performed at an extremely high rate of 3500 µm/min at a PTFE target temperature of 200° C. Moreover, a PTFE thin film was formed at a high rate of 2.6 µm/min using SR ablation of PTFE. The chemical structure of the deposited film was similar to that of the PTFE target as determined from Fourier transform infrared absorption spectroscopy (FT-IR) analysis.

X-ray absorption near edge structure (XANES) spectra of the Diluted Magnetic Semiconductors (DMS) system Zn1-x Mn x S have been measured at the Zn LII,III-edges and of Zn1-x Y x S (Y = Mn, Fe, Co) at the S K-edge using total electron yield mode. The Zn LIII-edge results for Zn1-x Mn x S reveal a dramatic reduction in intensity of the first prominent feature, just above the edge, in the XANES spectra. Analysis of the S K-edge XANES spectra for Zn1-x Y x S revealed an increase in a pre-edge peak and a corresponding decrease in the first above-edge peak with increase in transition metal content in the alloys. These results are consistent with more S 3p- transition metal (Y) 3d(t2) hybridized states and less S 3p- Zn 4(s,p) and S 3p-Zn 3d hybridized states becoming available as transition metal content increases in the alloys.

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.

Photoabsorption cross sections and fluorescence excitation spectra of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) vapors have been studied in the 110–220 nm region using synchrotron radiation. For DMS, a new Rydberg series originating from the ns orbital is identified. A number of broad bands from DMDS are assigned as Rydberg transitions. Emissions from DMS and DMDS are assigned as the CH3( A - X ) band. For DMDS, another emission which is attributable to the S2(B-X) band appears in the excitation below 125 nm. Photodissociation processes forming the excited fragments are discussed.

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.

Vacuum UV photolyses of silane and chlorinated silanes were investigated by using rare gas resonance lamps. Strong emissions, from the A 2Δ→X 2Π transition of SiH and the 1P0→1D2 transition of Si were observed in the photolysis of SiH4 by Ar and Kr resonance lamps. It was suggested that the threshold energies for the appearance of both emissions were lower than the values obtained by the electron impact of SiH4 reported by Perrin et al. A new broad unstructured emission band in the region 300–400 nm was observed in the photolysis of SiH2Cl2 and SiHCl3 by Ar, Kr, and Xe lamps. The band was attributed to the A 1B1→X 1A1 transition of SiCl2 radicals from the measurement of the appearance energy of the emission by using synchrotron orbital radiation.

He(I) photoelectron spectra (PES) and photoabsorption cross sections were measured for Ga(CH 3 ) 3 and In(CH 3 ) 3 in the 106–270 nm range. For both compounds, absorption starts at around 260 nm. Using the binding energies determined from the PES data, the broad absorption bands observed for the trimethylmetals are assigned as n s-terminating Rydberg transitions of the outer orbital electrons.

The photoabsorption cross sections and fluorescence excitation spectra of CCl3 F and CCl2 F2 were measured using synchrotron radiation at 106–200 nm. The observed absorption bands were accounted for as Rydberg transitions. The emitters produced from the CCl3 F and CC12F2 photodissociative excitations were attributed to CClF(A 1A‘←X1 A’) and CF2 (A 1B1 →X 1A1 ) transitions, respectively, and their radiative lifetimes were determined to be 626 ± 28 and 58 ± 2 ns. The emission from the CClF(A) starts at 140 nm and increases to 9.1 Mb at 106 nm, and that for CF2 (A) was deduced to be 0.9 Mb at 104.8 nm. The onsets of the fluorescence suggest that the electronically excited CClF and CF2 radicals are formed by the atomic Cl elimination but not by molecular Cl2 releasing process.

Photoabsorption cross sections and fluorescence excitation spectra of methanethiol vapor have been measured in the 130–200 nm wavelength region using synchrotron radiation. Many sharp structures observed in the 130–180 nm region are classified into three Rydberg series. The fluorescence which starts to appear at 175.2±2.0 nm is attributed to the CH 3 S(A 2 A 1 -X 2 E) band. The photodissociation processes are discussed in accord with the CH 3 S(A-X) fluorescence observed.

Photoabsorption cross sections and fluorescence excitation spectra of CH 3 NCO, CH 3 NCS and CH 3 SCN vapor were measured in the vacuum ultraviolet using synchrotron radiation. Many sharp structures observed from CH 3 NCO and CH 3 SCN in the 120–180 nm region are classified into three Rydberg series and their vibrational progressions, whereas for CH 3 NCS six broad bands exhibit no fine structure. The emission which starts to appear at 172.8 ± 1.0 nm excitation of CH 3 NCO is attributed to the NCO(A 2 Σ + -X 2 Π) band. The emissions from CH 3 NCS and CH 3 SCN are assigned to the A 2 Π-X 2 Π and B 2 Σ + -X 2 Π bands of NCS; the CN(B 2 Σ + -X 2 Σ + ) band is also observed at 125 nm excitation of CH 3 SCN. The photodissociation processes are discussed in accord with the emission observed.

The photoabsorption cross section and fluorescence excitation spectrum of S 2 Cl 2 vapor were measured in the range 110–200 nm using synchrotron radiation. A number of broad bands observed in the 120–170 nm region are assigned as Rydberg transitions. The fluorescence which starts to appear at 155.0±1.6 nm is attributed to the S 2 (B 3 Σ u − -X 3 Σ g − ) band. As for the of emitting species, the process of S 2 (B) + 2Cl is predominant for excitation in the 120–155 nm region, whereas another emission appears below 130 nm.

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.

We report here the first spectroscopic observation of the nπ* singlet states in gas‐phase polycyclic monoazines.

The photo-assisted etching of heavily phosphorous-doped polycrystalline silicon by chlorine was studied using synchrotron radiation as an extreme ultraviolet (EUV) light source. The quantum yield for the removal of the Si atoms at a chlorine pressure of 0.3 Torr was found to be about 0.5% photon-1 using the Ti-filtered light, which is mostly in the EUV region, 1-20 nm. Formation of electronically excited Cl+ ions upon EUV irradiation was confirmed by emission spectroscopy. Negative bias applied to the Si crystal was found to increase the etch rate.