Richard R. Smardzewski

Infrared spectroscopic evidence for matrix isolated ``nitrosyl hypofluorite,'' an isomer of nitryl fluoride

The in situ photolysis of molecular fluorine and NO2 molecules in nitrogen matrices at 8°K yields the FN‐bonded nitryl fluoride, FNO2, as the primary reaction product. However, controlled fluorine atom diffusion at 20°K, in the absence of photolytic radiation, results in the formation of the highly reactive, FO‐bonded, nitrosyl hypofluorite, ONOF. Infrared absorptions at 1716.4, 1199.9, 702.3, and 411.9 cm−1 were assigned to this species, which was shown from 15N and 18O isotopic studies to contain two nonequivalent oxygen atoms. The ONOF molecule undergoes intramolecular photorearrangement at wavelengths below 400 nm to produce the more stable FNO2 form.

Matrix reactions of oxygen atoms with H2S molecules

Ultraviolet and laser photolysis of dilute argon matrix samples containing O3 and H2S molecules at 8°K produced new infrared absorptions at 3425.0, 1177.0, 763.0, and 444.8 cm−1 which were assigned to the previously unobserved HSOH intermediate species, hydrogen thioperoxide. The HSOH molecule is believed to be formed by the following reaction in the argon matrix cage; {O+H2S→[H2S=O]→HSO+H→HSOH}cage. Extensive 18O and deuterium isotopic studies had shown this species to contain one oxygen atom and two nonequivalent hydrogen atoms, while the observation of the S–O stretching vibration at 763.0 cm−1 had confirmed the presence of a sulfur–oxygen single bond. The intense blue‐violet chemiluminescence which appeared when the photolyzed matrix samples were warmed to 20°K was subsequently identified as SO2 phosphorescence (3B1→1A1). Fluorescence from 1B1→1A1 was not observed.

Infrared spectra and characterization of the products of fluorine atom reactions with matrix isolated NO molecules

Simultaneous matrix deposition of F2 and NO molecules at high dilution in argon and nitrogen onto an 8°K CsI window produces three new infrared absorptions in addition to those of normal, FN‐bonded nitrosyl fluoride, FNO. The infrared features at 1886.6, 734.9, and 492.2 cm−1 (Ar matrix) and their 15N and 18O isotopic counterparts were assigned to the previously unobserved FO‐bonded isomer NOF, which appears to be a bent molecule having a molecular geometry similar to that of nitrosyl fluoride. Controlled fluorine atom diffusion at 20°K, in the absence of photolytic radiation, results in increased yields of the NOF molecule, while matrix photolysis experiments at 8°K have established that this species undergoes intramolecular photorearrangement to the more stable FNO form when exposed to radiation comprised of wavelengths below 280 nm.

The reaction of transition metal atoms with arenes: low temperature π-complex formation

Abstract Benzene, benzene- d 6 , and fluorbenzene were found to react with chromium, iron, cobalt, and nickel atoms upon co-deposition without diluents at 77 K or diluted in argon matrices at 10 K. Infrared studies of the co-condensation products indicate that the initial reaction of these transition metal atoms with an aromatic system is π-complex formation. Studies of concentration effects show that the chromium atom reaction is approximately second-order with respect to benzene, as expected, while the iron, cobalt, and nickel atom reactions appear to be first-order with respect to benzene concentration. The stoichiometry of these complexes was determined by co-deposition of the metal vapors with benzene/benzene- d 6 or benzene/fluorobenzene mixtures. Also, the relative strengths of the metalarene bonds were determined to be Cr τ Fe τ Co τ Ni. Manganese atoms were found not to react with benzene under these conditions.

Matrix reactions of copper atoms and ozone molecules. Infrared spectrum of CuO

The matrix reactions of copper atoms with ozone have been studied by infrared spectroscopy. Two products were found in the initial deposit: CuO3, which has a strong absorption at 802.3 cm−1, and CuO, which has its main feature, corresponding to the 63Cu16O isotopic species, at 628.0 cm−1 in solid argon. Copper atom reactions with oxygen‐18‐enriched ozone samples were used to obtain species identifications. The CuO3 absorption was very similar in frequency and isotopic splitting behavior to alkali and alkaline earth metal ozonide species previously studied in matrices. The CuO frequency is in good agreement with gas phase measurements which put the ground state CuO vibrational fundamental at 631.3 cm−1. Temperature cycling of the Cu–O3 matrices leads to CuO4 formation by the secondary reaction of CuO with unreacted ozone.

Chemiluminescent matrix reactions of atomic oxygen, sulfur, and O(3P)+H2S

Optical multichannel techniques have been used to analyzed the visible chemiluminescence generated by diffusion‐controlled warmup (8→20 °K) of separate, uv‐photolyzed inert gas matrices containing O3, H2S, H2S+O2, and O3+H2S molecules. Oxygen atoms were observed to diffuse and recombine in solid argon at ∼17 °K to produce the intense Herzberg I band system of molecular O2 (A→X) which was also observed in krypton though not in xenon matrices. The lack of any detectable emission in xenon was attributed to premature diffusion and depletion of atomic oxygen prior to diffusion‐controlled warmup. Matrix diffusion and recombination of sulfur atoms produced intense S2 emission (B→X) in all three matrices (Ar, Kr, Xe). Long, structured vibrational progressions (0,ν″) were observed in argon and krypton, while a broad, relatively structureless emission was observed in xenon. Suggested mechanisms for this latter effect include such processes as vibrationally unrelaxed fluorescence and/or S2*–Xe van der Waals ’’comple...

Matrix reactions of chlorine atoms with NO2 molecules

Matrix reactions of chlorine atoms with NO2 molecules diluted in argon yielded Cl–N bonded nitryl chloride ClNO2 as well as the Cl–O bonded isomer nitrosyl hypochlorite ClONO. Infrared absorptions at 1714.1, 855.6, 398.0, and 390.4 cm−1 were assigned to the ClONO species, which was shown from nitrogen‐15 and oxygen‐18 isotopic studies to be comprised of two weakly coupled diatomic radicals ClO and NO. Infrared spectroscopic evidence also suggested the presence of a third isomer OClNO which is produced by the insertion of a chlorine atom into an N–O bond of NO2 as well as by the direct maxtrix combination of ClO and NO radicals. The photolytic behavior of the ClONO species indicates that it undergoes intramolecular rearrangement, in the argon matrix cage, to produce the more stable ClNO2 form via a two‐step process which involves the OClNO molecule as an intermediate.

Vacuum ultraviolet photolysis of sulfur hexafluoride and its derivatives in argon matrices. The infrared spectrum of the SF5 radical

Vacuum ultraviolet photolysis at 1048, 1067 A of sulfur hexafluoride and its derivatives, SF5X (where X=Cl, Br, and SF5) in dilute argon matrices at 8 K produced two new infrared absorptions at 811.6 and 552.1 cm−1 which were also observed in the argon matrix reactions of fluorine atoms with SF4 molecules. Both features were assigned to the SF5 radical, a new species of C4v symmetry. A weaker absorption at 682.4 cm−1 was tentatively assigned to the SF3 radical, while, in the sulfur–fluorine experiments, secondary reactions produced the known SF−5 anion. The photolytic production of significant yields of SF4 and XF indicated the presence of a simultaneous molecular photoelimination process which, in the case of SF5Br, afforded the direct observation of the BrF fundamental at 650.5 cm−1.

Chemiluminescent reactions of sulfur atoms and oxygen atoms in solid argon matrices. SO chemiluminescence

When dilute argon matrices containing H2S+O3, OCS+O3 and H2S+NO2 molecules are exposed to ultraviolet radiation and subsequently allowed to warm from 8 to ∼20°K, several intense visible emissions with extensive vibrational structure appear. Besides those emissions of O2, S2, and SO2, two new luminescent systems are evident. Extensive oxygen‐18 and deuterium isotopic studies demonstrated the absence of hydrogen and the presence of a single oxygen atom in the emitting species of both systems, while matrix concentration studies established that the excited state species was an intermediate in SO2 formation, presumably molecular SO. The more intense of the two systems is located between 490–870 nm and contains up to ten members. The low values calculated for T0=22 543 cm−1 and ωe″=1130.7 cm−1 suggest that this transition is most likely SO (c1Σ−→ a 1Δ). A second, weaker emission system of SO with approximately eight members was found between 385–600 nm. T0 for this latter system was estimated at 28 400±1150 cm...

Surface‐enhanced Raman scattering from vapor‐deposited copper, silver, and gold. Excitation profiles and temperature dependence

Surface‐enhanced Raman spectra (SERS) of pyridine adsorbed on copper, silver, and gold films vapor deposited on low temperature substrates are reported. Similar spectra were also obtained on a sputter‐cleaned silver single crystal. Excitation spectra (450–750 nm) for all three metals revealed an overall increase in SERS activity at longer wavelengths, the relative increase being greater for copper and gold than silver. A broad excitation maximum near 2 eV was observed for the 1006 cm−1 pyridine SERS signal on silver. A lesser‐defined maximum was revealed for copper in the same general vicinity (1.7–2.0 eV) while a broad onset extending below 1.7 eV was observed for gold. Temperature studies (15–300 K) indicate that the observed SERS originate from molecular pyridine chemisorbed to the metal surfaces. In the cases of copper and gold, SERS were also observed from samples maintained at room temperature in vacuum. The intensities of the SERS signals were proportional to incident (cw) laser power at low power ...