Far-UV absorption spectra of SiH and dibridged SiH isolated in solid argon.

We employ electron bombardment during the deposition of an Ar matrix containing a small proportion of SiH to generate various silicon hydrides. Subsequently, the irradiation of a matrix sample at 365 nm decomposes SiH and dibridged SiH in solid Ar, which we identify through infrared spectroscopy. We further recorded the corresponding ultraviolet absorption spectra at each experimental stage.

Formation of -HO by Vacuum-UV Photolysis of O in Solid Hydrogen: Implication for Astrochemistry.

The observation that the to ratio (OPR) of interstellar HO is smaller than 3 is an important yet unresolved subject in astronomy. We irradiated O embedded in solid H at 3 K with vacuum-ultraviolet (VUV) light and observed IR lines associated with -HO (denoted as HO) and nonrotating HO-(H) (where H denotes -H) but no lines associated with -HO (denoted as HO). After maintaining the matrix in darkness for ∼30 h, the amount of HO decreased, accompanied by an increase in HO-(H) via diffusion of H.

Infrared Spectra of 1-Quinolinium (CHNH) Cation and Quinolinyl Radicals (CHNH and 3-, 4-, 7-, and 8-HCHN) Isolated in Solid Hydrogen.

Large protonated polycyclic aromatic hydrocarbons (HPAH) and the corresponding nitrogen heterocycles (HPANH) have been proposed as possible carriers of unidentified infrared (UIR) emission bands from galactic objects. The nitrogen atom in HPANH is expected to induce a blue shift of the band associated with the CC-stretching mode of HPAH near 6.3 μm so that their emission bands might agree better with the UIR band near 6.

IR absorption spectra of aniline cation, anilino radical, and phenylnitrene isolated in solid argon.

Electron bombardment of aniline (PhNH) in an Ar matrix mainly generated the aniline cation (PhNH), anilino (PhNH) and phenyl (Ph) radicals, and phenylnitrene (PhN). Further irradiation of the electron-bombarded matrix sample at 365 nm depleted PhNH and PhN, and resulted in the formation of PhNH, PhNH, and Ph. In separate experiments, irradiation of the PhNH/Ar matrix samples at 265 or 160 nm mainly generated PhNH and Ph radicals, but without the formation of PhNH and PhN.

Far-UV spectroscopy of mono- and multilayer hexagonal boron nitrides.

Hexagonal boron nitrides (hBNs) have a very high luminescence efficiency and are promising materials for deep-UV emitters. Although intense deep-UV emissions have been recorded in various forms of hBN excited by photons or energetic electrons, information on the electronic structure of the conduction band has been derived mainly from theoretical works. Therefore, there is a lack of high-resolution absorption data in the far-UV region.

IR absorption spectra of hexafluorobenzene anions and pentafluorophenyl radicals in solid argon.

Hexafluorobenzene anions (HFB) and pentafluorophenyl radicals (PFP) were generated by the electron bombardment of a HFB/Ar sample during matrix deposition. Further irradiation of the matrix sample at 365 nm detached the electron from HFB and produced its neutral counterpart HFB in solid Ar. Secondary photolysis of the matrix sample at 160 nm destroyed HFB and generated HFB and PFP.

Formation and IR spectrum of monobridged SiH isolated in solid argon.

The infrared (IR) spectrum of monobridged SiH (denoted as mbr-SiH) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm, 971.5 cm, 999.

Infrared Spectra of the 1-Methylvinoxide Radical and Anion Isolated in Solid Argon.

The 1-methylvinoxy radical (1-MVO) is an important intermediate in the combustion and tropospheric reaction of OH. However, the vibrational structures of this species and its anionic form, 1-methylvinoxide anion (1-MVO), are not fully known. Thus, in this study, we obtained the infrared (IR) absorption spectra of 1-MVO and 1-MVO trapped in a solid Ar matrix.

Direct IR Absorption Spectra of Propargyl Cation Isolated in Solid Argon.

The direct infrared (IR) absorption spectra of propargyl cations were recorded. These cations were generated via the electron bombardment of a propyne/Ar matrix sample during matrix deposition. Secondary photolysis with selected ultraviolet (UV) light was used for grouping the observed bands of various products.

Formation and identification of borane radical anions isolated in solid argon.

The infrared (IR) spectrum of borane(3) anions (BH) isolated in solid Ar was recorded; two vibrational modes were observed at 2259.4 and 606.6 cm, which were assigned to the BH stretching (ν) and out-of-plane large-amplitude (ν) modes, respectively.

UV absorption spectrum of allene radical cations in solid argon.

Electron bombardment during deposition of an Ar matrix containing a small proportion of allene generated allene cations. Further irradiation of the matrix sample at 385 nm destroyed the allene cations and formed propyne cations in solid Ar. Both cations were identified according to previously reported IR absorption bands.

Direct infrared observation of hydrogen chloride anions in solid argon.

To facilitate direct spectroscopic observation of hydrogen chloride anions (HCl), electron bombardment of CHCl diluted in excess Ar during matrix deposition was used to generate this anion. Subsequent characterization were performed by IR spectroscopy and quantum chemical calculations. Moreover the band intensity of HCl decays slowly when the matrix sample is maintained in the dark for a prolonged time.

Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon.

Hypervalent molecules are one of the exceptions to the octet rule. Bonding in most hypervalent molecules is well rationalized by the Rundle-Pimentel model (three-center four-electron bond), and high ionic bonding between the ligands and the central atom is essential for stabilizing hypervalent molecules. Here, we produced one of the simplest hypervalent anions, HF, which is known to deviate from the Rundle-Pimentel model, and identified its ro-vibrational features.

Infrared spectra of ovalene (CH) and hydrogenated ovalene (CH˙) in solid para-hydrogen.

We report the infrared (IR) spectra of ovalene (CH) and hydrogenated ovalene (CH˙) in solid para-hydrogen (p-H). The hydrogenated ovalene and protonated ovalene were generated from electron bombardment of a mixture of ovalene and p-H during deposition of a matrix at 3.2 K.

Photochemistry and infrared spectrum of single-bridged diborane(5) anion isolated in solid argon.

Three-center two-electron bonds are important for understanding electron-deficient molecules. To examine such a molecule, we produced a diborane(5) anion with a single-bridged structure upon electron bombardment during matrix deposition of Ar containing a small proportion of diborane(6). The diborane(5) anion was destroyed upon photolysis at 180, 220, 385, and 450 nm, but not at 532 nm.

Infrared spectra of protonated coronene and its neutral counterpart in solid parahydrogen: implications for unidentified interstellar infrared emission bands.

Large protonated polycyclic aromatic hydrocarbons (H(+) PAHs) are possible carriers of unidentified infrared (UIR) emission bands from interstellar objects, but the characterization of infrared (IR) spectra of large H(+) PAHs in the laboratory is challenging. IR absorption spectra of protonated coronene (1-C24 H13 (+) ) and mono-hydrogenated coronene (1-C24 H13 (.) ), which were produced upon electron bombardment of parahydrogen containing a small proportion of coronene (C24 H12 ) during matrix deposition, were recorded.

Infrared Spectra of Protonated Pyrene and Its Neutral Counterpart in Solid para-Hydrogen.

Protonated polycyclic aromatic hydrocarbons (H(+)PAHs) have been reported to have infrared (IR) bands at wavenumbers near those of unidentified infrared (UIR) emission bands from interstellar objects. We produced 1-C16H11(+) and 1-C16H11 upon electron bombardment during matrix deposition of p-H2 containing pyrene (C16H10) in a small proportion. Intensities of absorption features of 1-C16H11(+) decreased after the matrix was maintained in darkness or irradiated with light at 365 nm, whereas those of 1-C16H11 increased.

Formation and infrared absorption of protonated naphthalenes (1-C10H9+ and 2-C10H9+) and their neutral counterparts in solid para-hydrogen.

Protonated naphthalene (C(10)H(9)(+)) and its neutral counterparts (hydronaphthyl radicals, C(10)H(9)) are important intermediates in the reactions of aromatic compounds and in understanding the unidentified infrared (IR) emissions from interstellar media. We report the IR spectra of 1-C(10)H(9)(+), 2-C(10)H(9)(+), 1-C(10)H(9), and 2-C(10)H(9) trapped in solid para-hydrogen (p-H(2)); the latter three are new. These species were produced upon electron bombardment of a mixture of naphthalene (C(10)H(8)) and p-H(2) during matrix deposition.

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen.

We use protonated benzene (C(6)H(7)(+)) and cyclohexadienyl radical (c-C(6)H(7)) to demonstrate a new method that has some advantages over other methods currently used. C(6)H(7)(+) and c-C(6)H(7) were produced on electron bombardment of a mixture of benzene (C(6)H(6)) and para-hydrogen during deposition onto a target at 3.2 K.

Infrared absorption spectra of t-HNOH radicals generated on VUV irradiation of NO in solid hydrogen.

Photoproduct signature: Irradiation of solid hydrogen near 3 K containing NO with vacuum-UV light from synchrotron radiation yields new infrared absorption lines at 1241.7, 1063.6 and 726.

Direct spectral evidence of single-axis rotation and ortho-hydrogen-assisted nuclear spin conversion of CH3F in solid para-hydrogen.

Observation of two weak absorption lines from the E (K = 1) level and one intense feature from A (K = 0) for degenerate modes nu(4) and nu(6) of CH(3)F provides direct spectral evidence that CH(3)F isolated in p-H(2) rotates about only its symmetry axis, and not about the other two axes. An interaction between A and E vibrational levels caused by the partially hindered spinning rotation is proposed. Conversion of nuclear spin between A and E components of CH(3)F is rapid when p-H(2) contains some o-H(2), but becomes slow when the proportion of o-H(2) is much decreased.

Infrared absorption spectra of vinyl radicals isolated in solid Ne.

Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.

Photoabsorption cross sections of NH3, NH2D, NHD2, and ND3 in the spectral range 110-144 nm.

Cross sections for photoabsorption of NH3, NH2D, NHD2, and ND3 near 298 K were measured in the spectral range of 110-144 nm using radiation from a synchrotron. Absorption cross sections and oscillator strengths of NH3 agree satisfactorily with previous reports; those of ND3 are improved over those in a previous report, whereas those of NH2D and NHD2 are new. The oscillator strengths of transitions to D, D', D", F, and G states are nearly the same among all four isotopic variants, but those to D''' and E states vary substantially.

Experimental and theoretical investigation of rate coefficients of the reaction S(3P)+OCS in the temperature range of 298-985 K.

The reaction S(3P)+OCS in Ar was investigated over the pressure range of 50-710 Torr and the temperature range of 298-985 K with the laser photolysis technique. S atoms were generated by photolysis of OCS with light at 248 nm from a KrF excimer laser; their concentration was monitored via resonance fluorescence excited by atomic emission of S produced from microwave-discharged SO2. At pressures less than 250 Torr, our measurements give k(298 K)=(2.