bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Spectra and Electronic Structure of TCNQ Complexes
Authors: Tanaka Jiro , Tanaka Masashi , Kawai Takashi , Takabe Teruhiro , Maki Osamu 
Published: July 2006

Abstract
Electronic spectra of several TCNQ, complexes have been measured with single crystals by the transmission method. The assignment of electronic transitions are presented based on the electronic structure of the crystals. The molecular viewpoint is stressed in a theoretical treatment. The spectra are interpreted in terms of the charge transfer between TCNQ species and the local transitions of TCNQ and the donor molecules. It is shown that the electronic structure of the crystal may be deduced from the spectral analysis. The magnetic and electric properties of several conducting TCNQ complexes are discussed by this model with the wavefunctions determined by a theoretical calculation and the analysis of the spectral results.
Flotation of MnO4− and Fe3+ Ions by the Combined Use of Sodium Silicate and Cationic Surfactant
Authors: Takayanagi Isao , Kobayashi Koichi , Hachisuka Keiko , Sasaki Tsunetaka 
Published: July 2006

Abstract
The removals of MnO4− and Fe3+ ions from an aqueous solution by the combined use of silicate ions(SiO32−) and a cationic surfactant, hexadecyltrimethylammonium chloride (HTAC), were studied by means of ion flotation techniques. The effect of variables such as pH, the surfactant concentration, and the order of addition of the reagents on the floatability of the ions were studied. More than 98 and 97% of the MnO4− and Fe3+ ions, respectively, could be floated under the optimum conditions. The optimum composition of SiO32− and HTAC was found to be about 0.9 in mole fraction of SiO32− for both systems. It was also found that the order of the addition of the reagents markedly affects the floatability. Further, a schematic model of flotation was proposed, taking account of the compositions of the sublate. MnO4− and Fe3+ ion flotations differed from each other in that MnO4− ions combine with SiO32− ions through the double layer of HTAC molecules, which are subsequently coagulated and floated by HTAC, while Fe3+ ions or polynuclear Fe3+ ions combine directly with SiO32− ions, which are subsequently coagulated and floated by HTAC.
Aminosugars. XXVI. Synthesis of Amido-bonded Disaccharides Containing Hexosaminuronic Acids
Authors: Yoshimura Juji , Ando Hiroaki , Sato Tadahide , Tsuchida Shigeru , Hashimoto Hironobu 
Published: July 2006

Abstract
Synthesis and properties of amido-bonded disaccharides containing hexosaminuronic acids are described. The amino group of d-gluco- and d-mannosamine derivatives was acylated with d-gluco- and d-mannosaminuronic acid derivatives by the dicyclohexylcarbodiimide method, and the protecting groups of a few products were removed. Some of them showed the additive patterns of components in their PMR spectra.
Synthesis of 3,4-Di-O-acetyl-6-azido-2,6-dideaxy-2-(2′,4′-dinitroanilino)-α-d-glucopyranosyl Chloride
Authors: Ogawa Seiichiro , Fujimori Hitoshi , Suami Tetsuo 
Published: July 2006

Abstract
The title compound has been prepared as an intermediate for the chemical synthesis of glycosides of 2,6-diamino sugar.
Syntheses of Some Alkoxy-, Dialkoxy-, and Alkoxyamino-sulfonium Ions and Their O-Methylene and N-Methylene PMR Chemical Shifts
Authors: Minato Hiroshi , Yamaguchi Kei , Okuma Kentaro , Kobayashi Michio 
Published: July 2006

Abstract
Alkylation of sulfenates proved to be a good method for synthesis of alkoxysulfonium ion not obtainable by alkylation of sulfoxides. Dialkoxy- and alkoxyamino-sulfonium ions were prepared by alkylation of sulfinates and sulfinamides. Ethoxy- and methoxymorpholinophenylsulfonium tetraphenylborates were obtained as high-melting crystals, which almost quantitatively alkylated amines at room temperature. PMR spectra of RR′\overset⊕S–OCHAHBR″ and RR′\overset⊕S–N(R″)CHAHBR'″ were determined, and the relationship between δA–δB and (R,R′) were examined.
Solvent Extraction Equilibria of Acids. IV. Tetrachloroferric Acid in a Hexane Containing Trioctylphosphine Oxide-Aqueous Chloride Solution System
Authors: Sekine Tatsuya , Zeniya Yoshiyuki , Niitsu Masaru 
Published: July 2006

Abstract
From the distribution ratio of iron(III) between hexane containing trioctylphosphine oxide (TOPO) and a 4 mol dm−3 aqueous (H, Na)Cl solution, the extraction constants for the two complexes, Kex8=[FeCl3(TOPO)2]org–[Fe3+]−1[Cl−]−3[TOPO]org−2 and Kex4=[HFeCl4(TOPO)2]org–[Fe−3]−1[Cl−]−4[TOPO]org−2, were determined to be 104.5 and 104.3, respectively. The extractability of tetrachloroferric acid are discussed by comparing the Kex value with that for perchloric acid.
Reduction of α,β-Unsaturated Nitrile to Saturated Nitrile with Sodium Borohydride
Authors: Toda Fumio , Kanno Mutsushi 
Published: July 2006

Abstract
α,β-Unsaturated nitrile (1) was easily reduced to saturated nitrile (2) with sodium borohydride. Phenyl- (7a) and 2-phenanthryl-cyanoacetylene (7b) were also reduced with sodium borohydride to the saturated nitriles, 8a and 8b, respectively.
Photochemical Reduction of 2,3-Dihydro-2,3-methano-1,4-naphthoquinones with Xanthene
Authors: Maruyama Kazuhiro , Tanioka Soji 
Published: July 2006

Abstract
Photochemical reduction of 2,3-dihydro-2-methyl-2,3-methano-1,4-naphthoquinone (1a) and 2,3-dihydro-2,3-dimethyl-2,3-methano-1,4-naphthoquinone (1b) with xanthene was investigated. 6,7,8,9-Tetrahydrobenzocycloheptene-5,9-dione derivatives and stereochemical isomers of the so-called “1,2-adducts” of xanthene to carbonyl groups were isolated as the reaction products. CIDNP technique was applied for the examination of the course of the reactions.
Studies on Heterocyclics. V. Synthesis of Thiazolotriazepines
Authors: Mahajan M P , Sondhi S M , Ralhan N K 
Published: July 2006

Abstract
The possible psychosedative, bridgehead thiazolo[2,3-c]-1,2,4-triazepines have been synthesized by the condensation of 2-hydrazinothiazoles with β-chloropropionyl chloride.
The Crystal and Molecular Structure of an Anti-inflammatory Agent, 1-(Cyclopropylmethyl)-4-phenyl-6-methoxy-2(1H)-quinazolinone(SL-573)
Authors: Kimura Michio , Hirohashi Toshiyuki , Yamamoto Hisao 
Published: July 2006

Abstract
The crystal structure of the title compound (SL-573), crystallized from an ethyl acetate solution, has been determined by the single-crystal X-ray diffraction method. The crystals are monoclinic, with the space group P21/a, and these cell constants: a=17.395(11), b=8.371(5), c=10.871(7) Å, β=99°56(4)′, and Z=4. The intensities were measured visually from equi-inclination integrated Weissenberg photographs taken with Cu Kα radiation. The structure was solved by the symbolic addition method. The final R factor was 0.119 for 3284 reflections. The molecules are placed in pairs around the centers of symmetry and are linked by van der Waals’ distances less than 3.94 Å. The dihedral angle between the quinazoline and phenyl ring planes was found to be 42.8°.
Analysis of the Effect of Added Electrolyte on the Micellar Catalysis
Authors: Shirahama Keishiro 
Published: July 2006

Abstract
The effect of added electrolyte on micelle-catalyzed reaction was analyzed. The log [L.S] vs. log (total counter ion concentration) plot gives a straight line, where [L.S] is a limiting slope on a rate-surfactant concentration plot at an infinitely dilute micellar concentration. The slope is related to the number and the magnitude of the Coulombic term that may be included in the concentration effect of reactants, and in the intrinsic micellar effect, or the relative stabilization of a transition state in the presence of micelles. The above treatment was applied to (1) the hydrolysis of trimethyl orthobenzoate in sodium dodecyl sulfate solution, (2) the fading reaction of Crystal Violet in hexadecyltrimethylammonium bromide (CTABr) solution, and (3) the nucleophilic substitution reaction of 2,4-dinitrofluorobenzene in CTABr solution. It was found that the concentration effect is predominant in (1), while the relative stabilization of the transition state occurs in (2) and (3) in addition to the concentration effect.
Studies on 8,9,10,11-Tetrahydro-7H-cycloocta[de]naphthalenes. I. Conformations of 8,8,10,10-Tetrasubstituted Derivatives of 8,9,10,11-Tetrahydro-7H-cycloocta[de]naphthalene
Authors: Kamada Toshihiro , Wasada Nobuhide , Yamamoto Osamu 
Published: July 2006

Abstract
Several 8,8,10,10-tetrasubstituted 8,9,10,11-tetrahydro-7H-cycloocta[de]naphthalenes (3–9), novel pericyclic compounds of naphthalene, have been prepared through the alkylation reaction of 1,8-bis(bromomethyl)naphthalene and tetraethyl propane-1,1,3,3-tetracarboxylate, and the conformations of the cyclooctene ring in these compounds have been investigated on the basis of the PMR spectra. It is concluded that, at room temperature, the cyclooctene rings of (3–9) are frozen on the NMR time scale and exist exclusively in the boat form 15, which is shown to be the most energetically stable conformation for the peri-eight-ring systems from models. Some discussion is also given on the configurations of the substituent groups in (3–9).
A Mössbauer Study of Graphite Intercalated with Iron(III) Chloride and Aluminum Chloride
Authors: Tominaga Takeshi , Sakai Takuhiko , Kimura Tomohiko 
Published: July 2006

Abstract
The Mössbauer spectra of graphite–FeCl3 and graphite–FeCl3–AlCl3 compounds with varying FeCl3/AlCl3ratios were measured. At 298 K, the isomer shift of the Fe3+ peak of FeCl3 intercalated in the graphite–FeCl3 compounds was larger than that of pure anhydrous FeCl3, and two sets of Fe2+ quadrupole doublets appeared in the spectra of the graphite–FeCl3–AlCl3 compounds with FeCl3/AlCl3 ratios of approximately one or less. These results may be accounted for in terms of the transfer of graphite π-electrons to intercalated FeCl3.
Preparation of Some Alkylthallium(III) Dichlorides and Their Reactions with Potassium and Copper Halides
Authors: Uemura Sakae , Toshimitsu Akio , Okano Masaya 
Published: July 2006

Abstract
A simple synthesis is given for the stable monoalkylthallium(III) dichloride, C6H5CH(OR)CH2TlCl2 (1) from the corresponding diacetate (2) and potassium chloride in methanol or acetonitrile. 1(R=Me) reacts slowly with potassium and copper (I) halides to give mainly α-methoxystyrene and C6H5CH(OMe)CH2X (X=Cl, Br, I), respectively. It is concluded that 1(R=Me) is less susceptible than 2(R=Me) to SN1, SN2, and SNi reactions.
Kinetics of Oxidation of α-Hydroxy Acids by Ceric Sulfate
Authors: Tewari K C , Singh H N , Singh V S 
Published: July 2006

Abstract
The mechanism of the oxidation of α-hydroxy acids by ceric sulfate in sulfuric acid medium has been reexamined in the temperature range 15–30 °C and the thermodynamic parameters have been calculated. The role of HSO4− ion as an active inhibitor has been discussed quantitatively.
Dehydroannulenes. II. Syntheses of Diatropic Dimethyldiphenyl-and Tetraphenyl-tetrakisdehydro[18]annulenes
Authors: Katakami Tsutomu , Fukui Kunisuke , Okamoto Tetsuhiko , Nakagawa Masazumi 
Published: July 2006

Abstract
Syntheses of dimethyldiphenyl-(VI and XII) and tetraphenyltetrakisdehydro[18]annulenes (XVII) have been performed. It was found that the reaction sequence used for the synthesis of tetramethyltetrakisdehydro[18]annulene can be used generally for the preparation of tetrakisdehydro[18]annulenes having various substituents. The annulenes (VI, XII, and XVII) were found to be strongly diatropic having high conformational stability. Remarkable stability is provided by introduction of phenyl groups accompanied with decrease in solubility of the annulene. Dimethyldiphenyl derivative was prepared by two different routes which will lead to isomers (VI and XII) with respect to the relative positions of the diacetylene and hexapentaene linkages to the substituent groups. The isomers (VI and XII) can be regarded as presumably identical, but precise agreement of NMR and UV spectra could not be attained. Bathochromic shift of UV spectra of phenyl substituted annulenes compared with tetramethyl analogue indicated that phenyl groups exert prominent perturbation on the annulene system.
A Potentiometric Study on Complex Formation of Cadmium(H) and Lead(II) Ions with N-(2-Hydroxyethyl)ethylenediamine-N,N′,N′-triacetic Acid
Authors: Oyama Noboru , Shirato Takehide , Matsuda Hiroaki , Ohtaki Hitoshi 
Published: July 2006

Abstract
The complex formation of cadmium (II) and lead(II) ions with AT-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) has been studied potentiometrically in a 1.0 M NaClO4 medium at 25.0 °C by using glass and metal–amalgam electrodes. The emf data obtained over the pH range 1 to 10 were explained in terms of the formation of the following species: for the Cd–HEDTA system, CdL− (logβ101=13.21±0.04), CdhL (logβ111=15.61±0.02) and CdH2L+ (logβ121=16.68±0.04); for the Pb–HEDTA system, PbL− (logβ101=14.83±0.02), PbHL (logβ111=16.97±0.02),PbH2L+ (logβ121=17.89±0.02) and PbH3L2+ (logβ131=18.67±0.02), where βpqr=[MpHqLr(2p+q−3r)+/[M2+]p[H+]q[L3−]r and L denotes the unprotonated molecule of HEDTA. Protonation constants of HEDTA were determined as logβ011=9.20±0.01, logβ021=14.72±0.01, logβ031=17.06±0.01, logβ041=18.52±0.01 and logβ051=18.65±0.05.
Substrate Specificity in the Cyclodextrin-catalyzed Cleavage of Organic Phosphates and Monothiophosphates in Alkaline Solutions
Authors: Mochida Kazuo , Matsui Yoshihisa , Ota Yoshio , Arakawa Koji , Date Yoshio 
Published: July 2006

Abstract
Cyclodextrin accelerates the phenol release from organic phosphates such as dialkyl 4-nitrophenyl phosphates, but it decelerates the reactions of the corresponding monothiophosphates in alkaline solutions. Each reaction proceeds via the prior formation of a cyclodextrin–substrate inclusion complex, followed by the nucleophilic attack of the cyclodextrin alkoxide ion or the hydroxide ion on the reaction site of the included substrate. The equilibrium and kinetic parameters involved in the reaction processes were determined and discussed in connection with the geometry of a cyclodextrin–substrate complex.
N-Halogen Compounds of Cyanamide Derivatives. VI. The Preparation and Reaction of 2-Carbonimidoyl-3-imino-Δ4-1,2,4-thiadiazolines
Authors: Fuchigami Toshio , Odo Keijiro 
Published: July 2006

Abstract
The reactions of potassium methyl cyanoiminodithiocarbonate (I), potassium methoxy and ethoxythiocarbonylcyanamide (IIa and IIb) with N-chloroamidines in various solvents were investigated. Δ4,2,4-Thiadiazolines (TDZ), IIIa–d, were obtained from I in good yields, whereas the 1,3,5-triazines obtained as by-products in addition to TDZ were formed from II and N-chlorobenzamidine (NCB) in chloroform and dichloromethane. In the latter reaction, desulfrization occurred completely to give 1,3,5-triazine and/or a chain intermediate to 1,3,5-triazine in dipolar solvents. The TDZ were readily cleft at the N–S link by hydrogen sulfide and recyclized to 1,3,5-triazines. By alkaline hydrolysis, the TDZ were transformed to 2-amino-1,3,5-triazin-4-ols.
Arjungenin, Arjunglucoside I, and Arjunglucoside II. A New Triterpene and New Triterpene Glucosides from Terminalia arjuna
Authors: Honda Tadashi , Murae Tatsushi , Tsuyuki Takahiko , Takahashi Takeyoshi , Sawai Masanobu 
Published: July 2006

Abstract
Arjungenin, a new triterpene isolated from Terminalia arjuna, is shown to be 2α,3β,19α,23-tetrahydroxyolean-12-en-28-oic acid (1). The structures of two new triterpene glucosides, arjunglucoside I and arjunglucoside II, isolated from the same plant, were determined to be β-d-glucopyranosyl 2α,3β,19α,23-tetrahydroxyolean-12-en-28-oate (2) and β-d-glucopyranosyl arjunolate (3), respectively.
An Anion Radical Precursor in the Nucleophilic Substitution of o-Dinitrobenzene
Authors: Abe Takehiro , Ikegami Yusaku 
Published: July 2006

Abstract
By visible and ESR spectroscopies, the appearance of o-dinitrobenzene anion radical has been demonstrated for the replacement of one nitro group of o-dinitrobenzene by hydroxide ion in aqueous dimethyl sulfoxide. Kinetic studies have supported the suggestion that the anion radical is a precursor in the substitution reaction.
A General Synthetic Method for 1-Substituted 1,4-Dihydro-3(2H)-isoquinolinones
Authors: Kotake Hiroshi , Kinoshita Hideki , Inomata Katsuhiko , Masuda Hiroshi 
Published: July 2006

Abstract
The reaction conditions for the conversion of 3 into 4 were investigated in some detail, and it was found that the reductive animation of o-acylphenylacetic acid was allowed to proceed smoothly by the use of deactivated Raney nickel.
Microwave Spectrum, Structure, Dipole Moment and Internal Rotation of Ethanethiol. II. Gauche Isomer
Authors: Nakagawa Jun , Kuwada Kazunori , Hayashi Michiro 
Published: July 2006

Abstract
The microwave spectra of gauche-ethanethiol and its isotopic species were studied. Most of the observed spectra for the species having the plane of symmetry exhibited doublet structures with large spacings due to the internal rotation of the mercapto group. The rs structure of the gauche isomer was determined from the observed moments of inertia. The gauche isomer whose dihedral angle τ(CCSH) is 61°45′±58′ has structural parameters close to those for the trans isomer except the angles around the carbon atom in the methylene group. The difference in angle values around the carbon atom in the methylene group between the trans and gauche isomers can be explained by the 3°7′ tilt of the methylene group towards the lone pair electrons on the sulfur atom. The direction of the dipole moment in the molecule was discussed on the basis of data given by Schmidt and Quade. The potential barrier of the mercapto internal rotation was obtained from splittings of the observed spectra. The Fourier coefficients of this barrier are V1=−207±67, V2=−386±27, and V3=1305±20 cal/mol. The spectra due to the excited methyl and mercapto torsional states were also measured for the trans and gauche isomers. The potential barrier of the methyl internal rotation for the trans isomer was found to be 3260±30 cal/mol from splittings of the spectra due to the first excited methyl torsional state.
The Polarography of the Cadmium(II)–2-Carboxy-1-pyrrolidinecarbodithioate Chelate
Authors: Kitagawa Toyokichi , Nomura Kazuo 
Published: July 2006

Abstract
The electrochemical behavior of the cadmium(II) ion in the presence of 2-carboxy-1-pyrrolidinecarbodithioic acid (H2cpcd) as a chelating agent was investigated in an alkaline medium by d.c. polarography, a.c. polarography, cyclic voltammetry, and chronopotentiometry. The cadmium(II) chelate gave a reversible two-electron reduction wave at −0.86 V vs. SCE, with a postwave at −0.95 V. From the dependence of the total wave height on the mercury column height and from the methods of cyclic voltammetry, the electrode reduction of the cadmium(II) chelate was found to be diffusion-controlled. The diffusion current constant was 2.42 μA mol−1 m3 mg−2⁄3 s1⁄2. The postwave was identified as an adsorption wave of the cadmium(II) chelate from the dependence of the postwave height on the mercury column height, the a.c. peak height, the electrocapillary curves, and the results of chronopotentiometry. The surface excess of cadmium(II) chelate adsorbed on the mercury electrode was evaluated by means of three different electrochemical techniques. The composition of the cadmium(II)–cpcd chelate in the presence of excess H2cpcd was Cd(cpcd)22−, and the overall stability constant was estimated to be 8.0×1012 at 25.0 °C and μ=1.5.
XPS Study on the Charge Distribution in Chromium(0) Complexes
Authors: Kinomura Fumio , Tamura Tadashi , Watanabe Iwao , Yokoyama Yu , Ikeda Shigero 
Published: July 2006

Abstract
Binding energies of core electrons in Cr(C6H6)2, Cr(C6H6)(CO)3, and Cr(CO)6 were measured by means of X-ray photoelectron spectroscopic method in solid phase. By comparison with their UPS spectra observed in gasous phase, binding energies referred to vacuum level can be obtained. On the basis of this result, charge distribution in these complexes are estimated. The intramolecular relaxation energy of Cr(C6H6)2 is also discussed.
A Macrocyclic Enzyme Model System. An Electrostatic-Hydrophobic Double-Field Catalysis by a [20]Paracyclophane in the Deacylation of p-Nitrophenyl Hexadecanoate
Authors: Murakami Yukito , Aoyama Yasuhiro , Dobashi Kazuyuki , Kida Masaaki 
Published: July 2006

Abstract
The catalytic functions of 10-oxo[20]paracyclophanyl-22(23)-methyltrimethylammonium chloride (1) in the hydrolysis and aminolysis reactions of p-nitrophenyl hexadecanoate (PNPP) were investigated in 1%(v/v)methanol–1%(v/v)dioxane-water over the pH 9–10 region at 40.0 °C and μ=0.2 (NaCl) with the initial PNPP concentration of 1.00×10−5 M. The paracyclophane (0.88×10−5 M) accelerated the hydrolysis of PNPP by one order of magnitude at pH 9.7. The presence of either ethanolamine or glycine in the 1-catalyzed deacylation of PNPP resulted in further rate enhancement. The rate enhancement was brought about by the aminolysis reaction of PNPP with the amines as confirmed by the product analysis. The greater reactivity of glycine relative to that of ethanolamine was attributed to the electrostatic interaction between the anionic carboxylate group of glycine and the cationic ammonium group of 1. The novel electrostatic-hydrophobic double-field catalysis was discussed for the glycinolysis reaction.
Metal-Assisted Terpenoid Synthesis. IV. Nickel-Catalyzed Reactions of 1,3-Dienes with Ketones. A New Synthesis of Long Chain Tertiary Alcohols
Authors: Akutagawa Susumu 
Published: July 2006

Abstract
Catalytic reactions of 1,3-butadiene with ketones were carried out with a nickel-ligand system to give stereoselectively tertiary alcohols having a (2Z, 5E)-2,5,7-octatrienyl- or a (2Z, 6E, 9E)-2,6,9,11-dodecatetraenyl chain. Similar reactions of isoprene gave a mixture of terpenic and apoterpenic alcohols. A possible reaction scheme was discussed in terms of an insertion of the carbonyl group to a σ-allyl end of octadienyl or dodecatrienyl nickel complexes.
Formation of Excited Molecules and Atoms by Controlled Electron Impact on Hydrogen Chloride and Chlorinated Methanes
Authors: Toyoda Minoru , Ogawa Teiichiro , Ishibashi Nobuhiko 
Published: July 2006

Abstract
The dissociation, ionization, and excitation of hydrogen chloride and chlorinated methanes under controlled electron-impact excitation were studied at low pressures. The photoemissions (200–600 nm) were observed and assigned to HCl+, CH, CH+, CCl, H, and Cl+. Such species as H and HCl+ from HCl, and H and CH from CH2Cl2 were concluded to be produced by some one-electron processes. The photoemission of the HCl+ produced from CH2Cl2 increases quadratically with the electron-beam current; in this case HCl+ is mainly produced by the molecular elimination of HCl and the successive ionization excitation by the second electron. The threshold energies of the photoemissions were found to be 16.8 eV for HCl+* from HCl, 19.8 eV for H* from HCl, and 17.6 eV for CH*(A) from CHCl3. The processes of the excitation of these species near the threshold were discussed.
Formation of Diacetylene Ion (A2Πu) by Controlled Electron Impact on Unsaturated Molecules
Authors: Tsuji Masaharu , Ogawa Teiichiro , Imasaka Totaro , Nishimura Yukio , Ishibashi Nobuhiko 
Published: July 2006

Abstract
By the impact of an electron beam (100–450 eV) on aliphatic hydrocarbons (C2H2, C2H4, C4H6), cyclo-octadienes, and aromatic molecules (C6H6, C10H8, C12H10, etc.) at about 10−3Torr, the Schüler’s T spectrum of diacetylene ion (A2Πu–X2Πg) was observed in the 505–570 nm region, in addition to the well-known systems of H(Balmer), CH(A–X), and C2(Swan). Three different kinds of mechanisms for the formation of C4H2+ (A) were derived from the dependence of the emission intensity on the electron-beam current and the gas pressure: (a) the primary excitation process (C4H6), (b) the secondary excitation process (aromatic molecules, cyclooctadienes), and (c) the dimerization excitation process (C2H2, C2H4). The intensity ratio (C4D2+/C4H2+) of the T spectrum from C6H6 and C6D6 was 0.83±0.04 for the (0,0) sequence at 300 eV excitation.