Time-resolved Atomic Resonance Absorption Research Articles

Kinetic investigation of reactions of atomic carbon, C[2p 2( 3P J)], with simple nitrogen-containing molecules and aromatic heterocyclic compounds

The reactions of atomic carbon in its electronic ground state, C[2p 2( 3P J)], with some simple nitrogen-containing molecules and aromatic heterocyclic compounds have been investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultra-violet following the generation of C(2 3P J) by the pulsed photolysis of C 3O 2. Decay profiles for atomic carbon were derived from resonance absorption measurements at λ = 166 nm (3 3P J–2 3P J) using repetitive pulsing techniques coupled with signal averaging. Absolute rate data for the collisional removal of C(2 3P J) by these gases were obtained as follows: k R (cm 3 molecule −1 s −1, 300 K): NH 3 < 1.1 × 10 −1, 1-propanamine < 8.2 × 10 −12, 2-methylpyridine = 5.3 ± 0.6 × 10 −10, 4-methylpyridine = 5.5 ± 0.2 × 10 −10, 1-methylpyrrole = 2.3 ± 0.5 × 10 −10, thiazole = 2.9 ± 0.2 × 10 −10, oxazole = 2.4 ± 0.2 × 10 −10 and isoxazole = 2.2 ± 0.3 × 10 −10. The rate data were compared, where possible, with absolute rate data for analogous collision targets reported hitherto and considered within the context of the role of atomic carbon in the interstellar medium.

Kinetic studies of atomic carbon, C[2p 2( 3P J)], with small sulfur-containing molecules by time-resolved atomic resonance absorption spectroscopy in the vacuum ultra-violet

We present a kinetic investigation of the reaction of atomic carbon in its electronic ground, C[2p 2( 3P J)], with the small sulfur-containing molecules H 2S, OCS, SO 2 and CS 2 by time-resolved atomic spectroscopy in the vacuum ultra-violet following the generation of C(2 3P J) by the pulsed photolysis of C 3O 2. Decay profiles for atomic carbon were derived from resonance absorption at λ = 166 nm (3 3P J–2 3P J) using repetitive pulsing techniques coupled with signal averaging. Absolute rate data for the collisional removal of C(2 3P J) by these gases were obtained as follows: k R (cm 3 molecule −1 s −1, 300 K)—H 2S 2.5 ± 0.6 × 10 −10, OCS 5.6 ± 0.2 × 10 −11, SO 2 9.7 ± 0.3 × 10 −11 and CS 2 1.6 ± 0.4 × 10 −10. Rate data for the reaction of atomic carbon with the photochemical precursor, necessary as an absolute kinetic standard, were obtained yielding k(C 3O 2) = 1.8 ± 0.3 × 10 −10, in full agreement with previous investigations. The rate data in general were compared, where possible, with those derived from fast flow techniques and molecular beams for the particular case of H 2S where overall insertion has been demonstrated with the detection of HCS and where H atom abstraction would be endothermic. The results in general are considered within the context of C atom reactions with sulfur-containing species in the interstellar medium.

Kinetic Studies of Atomic Carbon, C[2p2 (3PJ)], with Thiols by Time-Resolved Atomic Resonance Absorption Spectroscopy in the Vacuum Ultraviolet

Reaction rates of atomic carbon in its electronic ground state, C[2p2 (3PJ)], with a range of large sulfur-containing molecules have been investigated using time-resolved atomic spectroscopy in the vacuum ultraviolet following pulsed irradiation. Absolute rate data for the collisional removal at 300 K of C(23PJ) by the gases 1-propanethiol, 1-butanethiol, 1-pentanethiol, 2-propanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol and dimethyl sulfide are reported. All processes proceed at rates of the order of the collision numbers, supporting an overall mechanism of C-atom insertion into the S–H bond following initial addition, which is energetically favourable, a mechanism demonstrated analogously hitherto with H2S and where H-atom abstraction would also be endothermic.

Kinetic measurements of fluorine, bromine and iodine atom-abstraction reactions at elevated temperatures by ground-state atomic rubidium, Rb(5 2S 1/2), studied by time-resolved laser-induced fluorescence

The kinetics of a range of halogen atom-abstraction reactions undergone by atomic rubidium in its electronic ground state, Rb(5 2S 1/2), have been investigated by time-resolved laser-induced fluorescence at elevated temperatures. Rb(5 2S 1/2) was generated in an excess of halogenated reactant and He buffer gas by pulsed photolysis of rubidium halide vapours. Two separate experimental systems were employed operating at the Rydberg transition at λ=420.2 nm {Rb[6p( 2P 3/2)]→Rb[5s( 2S 1/2)]} and at the shorter wavelength component of the spin-orbit resolved D-line doublet transition at λ=780.0 nm {Rb[5s5p( 2P 3/2)]→Rb[5s( 2S 1/2)]}. Second-order rate constants k RX for various F, Br and I abstraction reactions have been measured for essentially single-temperature conditions. These rate constants, which represent a new body of absolute rate data for Rb( 2S 1/2), are compared with the values reported hitherto by time-resolved atomic resonance absorption spectroscopy and with those previously obtained for other alkali metal atoms using time-resolved techniques.

Reactions of ground state atomic calcium, Ca[4s 2( [formula omitted])], investigated by time-resolved atomic resonance absorption spectroscopy at elevated temperature

Absolute second-order rate data at elevated temperature are reported for reactions of ground state calcium atoms, Ca[4s 2( 1 S 0 )], generated by broad band pulsed photodissociation of CaI 2 vapour in the presence of various reactants and excess helium buffer gas and monitored by time-resolved atomic resonance absorption spectroscopy at λ=422.673 nm ( Ca[4 p( 1 P 1)]← Ca[4 s 2( 1 S 0)] ). Unlike most previous time-resolved atomic resonance absorption measurements on ground state atomic calcium at this wavelength, complete decay profiles were recorded digitally in the ‘single-shot mode’ in the time-domain using resonance radiation from a highly intense microwave-powered sealed atomic emission source. The following second-order rate constants for the reactions of Ca( 1 S ) are reported: k R (cm 3 s −1 per molecule) (873 K), 1-C 3H 7Cl (3.5±0.1)×10 −12; 1-C 4H 9Cl (2.5±0.2)×10 −12; 1-C 5H 11Cl (2.2±0.4)×10 −12; 1-C 6H 13Cl (2.8±0.3)×10 −12; CHF 2Cl (4.8±0.2)×10 −12; and CH 3I (16.3±3.0)×10 −12 (errors 1 σ). These data are compared with analogous rate data for reactions of atomic calcium with other halides. Estimates are also reported for diffusion coefficients for Ca( 1 S 0 ) in various buffer gases, D 12 (cm 2 s −1) (STP): He, 0.47±0.05; Kr, 0.14±0.02; Xe, 0.09±0.02; and N 2, 0.26±0.02. These are found to be in sensible accord with analogous values of D 12 ( Ba( 1 S 0)+ He , Kr and Xe) derived hitherto by laser methods.

Measurements of the Rates of Reactions of Ground State Atomic Calcium, Ca[4s2(1S0)], with Alkyl Bromides at Elevated Temperature by Time-Resolved Atomic Resonance Absorption Spectroscopy [Ca(41P1 - 41S0); λ = 422.7 nm

We present a kinetic study of reactions of ground state atomic calcium, Ca[4

Collisional removal of atomic carbon, C[2p 2( 3P J)], by aldehydes and ketones, investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultra-violet

A kinetic study is presented of the collisional removal of ground state atomic carbon, C[2p 2( 3P J )], with various aldehydes and ketones in the gas phase following pulsed irradiation. The atomic carbon was generated by the photolysis of C 3O 2 ( λ > ca. 160 nm) in the presence of excess helium buffer gas and the added reactant gases in a slow flow system, kinetically equivalent to a static system, and monitored photoelectrically by time-resolved atomic resonance absorption spectroscopy in the vacuum ultra-violet at λ = 166 nm (3 3P J ← 2 3P J ) using signal averaging techniques. Absolute second-order rate constants ( k R/cm 3 molecule −1 s −1, 300 K) for the removal of C(2 3P J ) with these reactants were found to be as follows: formaldehyde 6.2 ± 0.3 × 10 −10; acetaldehyde 5.4 ± 0.3 × 10 −10; propionaldehyde 4.1 ± 0.3 × 10 −10; n-butyraldehyde 6.6 ± 0.3 × 10 −10; pentanal 4.6 ± 0.2 × 10 −10; hexanal 5.3 ± 0.4 × 10 −10; acetone 5.9 ± 0.3 × 10 −10; butanone 5.1 ± 0.2 × 10 −10; 2-pentanone 3.8 ± 0.2 × 10 −10; and 3-pentanone 4.6 ± 0.1 × 10 −10. No significant monotonic variation is thus observed in the rate data within these series of collisional processes where, from the similarity in the observed results, it is concluded that reaction is dominated by attack on the carbonyl group. The large values of these rate constants indicate that reactions of C(2 3P J ) with aldehydes and ketones, some of which have been observed by radio frequency spectroscopy in interstellar clouds and considered to be generated initially by hot atom reactions, are sufficiently rapid to be included in modelling of the interstellar medium.

The Gas-Phase Kinetics of Reactions of Alkali Metal Atoms with Nitric Oxide

Time-resolved atomic resonance absorption spectroscopy was employed, with flash-photolysis generation of atomic potassium and sodium at 734 K, to investigate the kinetics of K + NO + Ar and Na + NO + Ar. The low-pressure limit recombination rate constants are (1.0 ± 0.2) × 10-31 and (1.9 ± 0.5) × 10-32 cm6 molecule-2 s-1, respectively. Mainly ionic, triplet state adducts are predicted. RRKM modeling yielded K−NO and Na−NO bond dissociation enthalpies of 104 and 66 kJ mol-1, which compare well with UQCISD(T)/6-311+ G(2d) ab initio values of 81 and 68 kJ mol-1, respectively. For Li + NO +Ar, the predicted binding energy is 134 kJ mol-1, which yields a predicted rate constant of 1.4 × 10-31 cm6 molecule-2 s-1.

The Collisional Quenching of Electronically Excited Germanium Atoms, Ge[4p2(1S0)], with Olefins and Acetylenes Investigated by Time-resolved Atomic Resonance Absorption Spectroscopy

The Collisional Quenching of Electronically Excited Germanium Atoms, Ge[4p²(¹S₀)], with Olefins and Acetylenes Investigated by Time-resolved Atomic Resonance Absorption Spectroscopy

Collisional quenching of electronically excited germanium atoms, Ge[4p 2( 1S 0)], by small molecules investigated by time-resolved atomic resonance absorption spectroscopy

The collisional quenching of electronically excited germanium atoms, Ge[4p 2( 1S 0)], 2.029 eV above the 4p 2( 3P 0) ground state, has been investigated by time-resolved atomic resonance absorption spectroscopy in the ultraviolet at λ = 274.04 nm [4 d( 1 P 1 0) ← 4 p 2( 1 S 0)] . In contrast to previous investigations using the ‘single-shot mode’ at high energy, Ge( 1S 0) has been generated by the repetitive pulsed irradiation of Ge(CH 3) 4 in the presence of excess helium gas and added gases in a slow flow system, kinetically equivalent to a static system. This technique was originally developed for the study of Ge[4p 2( 1D 2)] which had eluded direct quantitative kinetic study until recently. Absolute second-order rate constants obtained using signal averaging techniques from data capture of total digitised atomic decay profiles are reported for the removal of Ge( 1S 0) with the following gases ( k R in cm 3 molecule −1 s −1, 300 K): Xe, 7.1 ± 0.4 × 10 −13; N 2, 4.7 ± 0.6 × 10 −12; O 2, 3.6 ± 0.9 × 10 −11; NO, 1.5 ± 0.3 × 10 −11; CO, 3.4 ± 0.5 × 10 −12; N 2O, 4.5 ± 0.5 × 10 −12; CO 2, 1.1 ± 0.3 × 10 −11; CH 4, 1.7 ± 0.2 × 10 −11; CF 4, 4.8 ± 0.3 × 10 −12; SF 6, 9.5 ± 1.0 × 10 −13; C 2H 4, 3.3 ± 0.1 × 10 −10; C 2H 2, 2.9 ± 0.2 × 10 −10; Ge(CH 3) 4, 5.4 ± 0.2 × 10 −11. The results are compared with previous data for Ge( 1S 0) derived in the single-shot mode where there is general agreement though with some exceptions which are discussed. The present data are also compared with analogous quenching rate data for the collisional removal of the lower lying Ge[4p 2( 1D 2)] state (0.883 eV), also characterized by signal averaging methods similar to that described here.

Reactions of atomic carbon, C[2 (3P J)],with dienes and diynes investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultraviolet

Absolute data for the collisional removal of ground-state atomic carbon, C[2 (3PJ)], generated by pulsed irradiation and monitored by time-resolved atomic resonance absorption spectroscopy in the vacuum ultraviolet, have been determined for reaction with a range of dienes and diynes. The precursor of atomic carbon was C3O2 (λ>ca. 160 nm), photolysed in the presence of excess helium buffer gas and the added reactant gases in a slow flow system, kinetically equivalent to a static system. C(23PJ) was then monitored photoelectrically at λ=166 nm (33PJ←23PJ) with data capture and signal averaging of complete atomic profiles by a transient digitiser with direct computer interfacing for kinetic analysis. The following absolute second-order rate constants (kR/c molecule-1 s-1, 300 K) for the reactions of ground-state carbon atoms with the various organic targets have been measured: allene, 8.0±0.1×10-10; buta-1,3-diene, 1.1±0.1×10-9; penta-1,4-diene, 1.2±0.1×10-9; hexa-1,5-diene, 1.2±0.1×10-9; hepta-1,6-diene, 1.2±0.1×10-9; octa-1,7-diene, 1.2±0.1×10-9; nona-1,8-diene, 1.3±0.1×10-9; deca-1,9-diene, 1.4±0.1×10-9; octa-1,7-diyne, 1.1±0.1×10-9; nona-1,8-diyne, 1.1±0.1×10-9. These absolute rate data are compared with data reported hitherto for the reaction of C(23PJ) with the analogous mono-alkenes and mono-alkynes. The large value of the rate constants for reactions of C(23PJ) with both the mono- and di-organic species indicate cross-sections which are sufficiently large to be included in the modelling of interstellar clouds characterised by low temperatures and densities, an aspect of this work which is considered.

Kinetic studies of fluorine atom abstraction by ground state atomic cesium, Cs(62S1/2), using time-resolved laser-induced fluorescence [Cs(72P3/2 - 62S1/2), λ = 455.5 nm] following pulsed irradiation

Absolute second-order rate data for fluorine atom abstraction by ground state atomic cesium, Cs(62S1/2), with the molecules SF6, CF3H, and CF4 are reported for elevated temperatures using time-resolved laser-induced fluorescence [CS(72P3/2 - 62S1/2), λ = 455.5 nm] following pulsed irradiation. The results are compared with previous measurements derived from time-resolved atomic resonance absorption spectroscopy in the “single-shot mode.”

Kinetic investigation of the collisional quenching of electronically excited germanium atoms, Ge(4p2(1D2)), with acetylenes studied by time-resolved atomic resonance absorption spectroscopy in the ultra-violet

Electronically excited germanium atoms, Ge(4p 2 ( 1 D 2 )), 0.883 eV above the 4p 2 ( 3 P j ) ground state, have been studied in the time-domain following their photochemical generation (λ> ca. 160nm) from Ge(CH 3 ) 4 in the presence of excess helium gas and a range of acetylenic reactant partners. Ge(4 1 D 2 ) was monitored photoelectrically in absorption using the resonance transition at λ=241.737 nm (Ge(4d( 1 D 2 ))). Absolute second-order rate constants (k R , errors 2σ) are reported for the collisonal removal of Ge (4 1 D 2 ) with the various acetylenic reactants. The collisional quenching of Ge(4 1 D 2 ) with 1,3-butadiene was also investigated in view of the comparison with earlier studies on the removal of silylenes and other Group IV atoms with both 2-butyne and this di-olefinic species. This yielded the absolute second-order rate constant, k R (Ge(4 1 D 2 ) + 1,3-butadiene, 300 K) = (8.0±0.4) x 10 −10 cm 3 molecule −1 s −1 . This resulting new body of absolute rate data for the low lying electronically excited germanium atom is compared with analogous data for the ground state, Ge(4p 2 ( 3 P J ), characterised hitherto by a related method using time-resolved measurements with signal averaging. The data are also considered within the context of the collisional behaviour of Group IV atoms overall with these acetylenes.

Collisional quenching of electronically excited germanium atoms, Ge(4p 2( 1D 2)), by unsaturated ring compounds determined by time-resolved atomic resonance absorption spectroscopy in the ultra-violet

The collisional quenching of the optically metastable, electronically excited germanium atom, Ge(4p 2( 1D 2)) (0.883 eV), by unsaturated ring compounds has been investigated by time-resolved atomic resonance absorption spectroscopy in the ultra-violet at λ = 241.737 nm Ge(4d( 1D 2°)) ← (4p 2( 1D 2))) following the pulsed irradiation (λ > ca. 160 nm) of Ge(CH 3) 4 in the presence of excess helium gas and the added reactant gases. The 1D 2 atom was generated in a slow flow system, kinetically equivalent to a static system and monitored photoelectrically using direct computer interfacing for data capture and analysis as described hitherto. Collisional quenching proceeds rapidly in all cases and the resulting new body of rate data are compared in general terms with absolute second-order rate constants for the removal of Ge(4 1D 2) by simple molecules and unsaturated hydrocarbons investigated hitherto and, where available, with data for the removal of the ground state Ge(4 3P j) and Si(3 3P j) atoms with similar species.

Kinetic studies of the reactions of ground state atomic carbon, [formula omitted], with halogenated methanes investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultra-violet

A kinetic investigation is presented of the reactions of ground state atomic carbon, C(2p 2( 3P J)) , with the molecules methyl chloride, methyl bromide, methyl iodide, methyl fluoride, dichloromethane, chloroform and carbon tetrachloride. Atomic carbon was generated by the repetitive pulsed irradiation (λ > ca. 160 nm) of C 3O 2 in the presence of excess helium buffer gas and the added reactant gases in a slow flow system, kinetically equivalent to a static system. C(2 3 P J ) was then monitored photoelectrically by time-resolved atomic resonance absorption in the vacuum ultraviolet (λ = 166 nm, 3 3 P J ← 2 3 P J ) with direct computer interfacing for data capture and analysis. The following absolute second-order rate constants for the reactions of C(2 3 P J ) with the above collision partners are reported (errors 2σ): Reactant k R/ cm 3 molecule −1 s −1 (300 K) CH 3Cl (4.5 ± 0.3) × 10 −12 CH 3Br (5.2 ± 0.3) × 10 −11 CH 3I (5.3 ± 0.3) × 10 −11 CH 3F (1.3 ± 0.1) × 10 −12 CH 2Cl 2 (5.9 ± 0.3) × 10 −12 CHCl 3 (8.9 ± 0.5) × 10 −12 CCl 4 (1.5 ± 0.1) × 10 −11 These yield, to the best of our knowledge, the first reported body of absolute rate data for reactions of ground state carbon with these reactants. Although a large body of absolute rate data for atomic silicon in its Si(3P 2( 3P J)) ground state has now been determined directly in recent years by time-resolved atomic resonance absorption spectroscopy in the ultraviolet itself with a wide range of collision partners, there are no analogous data for these particular reactants with which the data for C(2 3 P J ) may be compared. Estimates of the small energy barriers consistent with the rate data for C(2 3 P J ) + CH 3 Cl, Br, I coupled with the bond dissociation energies of these polyatomic reactants in particular confirms the values of the bond dissociation energies for CCl, Br, I derived from mechanistic interpretation on C 2 Swann band emission from alkali metal-organic halide diffusion flames.

The collisional behaviour of electronically excited germanium atoms, Ge(4p 2( 1D 2)), with simple molecules investigated by time-resolved atomic resonance absorption spectroscopy in the UV

The collisional behaviour is presented of electronically excited germanium atoms, Ge(4p 2( 1D 2)), 0.883 eV above the 4p 2( 3P J ) ground state, in the presence of a range of simple molecules. We have shown that the 1D 2 atom, which is optically metastable, may be produced photochemically in the pulsed mode and monitored by time-resolved atomic resonance absorption spectroscopy in the UV. The electronically excited germanium atoms are normally generated from the low-wavelength pulsed irradiation (γ ≳ 160 nm) of Ge(CH 3) 4 in the presence of excess helium gas and added reactant gases in a slow flow system, kinetically equivalent to a static system. This photochemical precursor yields higher densities of Ge(4 1D 2) for kinetic studies than GeCl 4 which is also used. The electronically excited atom was monitored photoelectrically in the repetitive mode by time-resolved atomic resonance absorption spectroscopy in the UV with direct computer interfacing for data capture and analysis. Ge(4 1D 2) was monitored using the resonance transition at γ = 241.737 nm (Ge(4d( 1D 2)) ← (4p 2( 1D 2))). The following absolute second-order rate constants ( k R, errors 2σ) are reported for the collisional removal of Ge(4 1D 2) with various collision partners (R): ▪ The resulting rate data are compared with analogous collisional data for Ge(4p 2( 1S o)) ( E=2.029 eV) reported from studies in the single-shot mode. In all cases, collisional removal of the 1D 2 state is significantly faster than the 1S 0 state. The rate data are also considered in the context of Group IV atoms in the low-lying np 2( 1D 2, 1S 0) metastable states, in terms of the nature of the potential surfaces involved on collision, on the basis of the weak spin—orbit coupling approximation and ( J, ω) coupling.

The collisional behaviour of ground state atomic carbon, C(2p2(3Pj) with ethylene and acetylene investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultraviolet

Abstract We present a kinetic study of the collisional behaviour of ground state atomic carbon, C(2p2(3PJ) with the molecules C3O2, C2H4 and C2H2. Atomic carbon was generated by the repetitive pulsed irradiation (λ>ca. 160 nm of C3O2 in a slow flow system and then monitored photoelectrically by time-resolved atomic resonance absorption in vacuum ultraviolet (λ= 166 nm, 33PJ←23PJ) with direct computer interfacing for data capture and analysis. The following absolute second-order rate constants for the reactions of C(23PJ) with the molecules C3O2, C2H4 and C2H2 were obtained: kR/cm3 molecule−1 s−1(300 K); C3O2 (1.8 ±0.1) x 10−10, C2H4(2.0±0.1) x 10−10 and C2H4(2.1±0.1) x 10−10. The result for C3O2 is in accord with earlier measurements. Those for C2H4 and C2H2 yield values at least six orders of magnitude faster than initial estimates from earlier indirect measurements on a flow system.

Absolute rate data for the reactions of ground-state atomic carbon, C[2p2(3P J )], with alkenes investigated by time-resolved atomic resonance absorption spectroscopy in the vacuum ultraviolet

The collisional behaviour of ground-state atomic carbon, C[2p2(3PJ)], monitored by time-resolved atomic resonance absorption spectroscopy, is reported for reactions with a wide range of alkenes. Atomic carbon was generated and studied in a modified vacuum ultraviolet experimental system similar to that employed hitherto by the repetitive pulsed irradiation (λ≳ 160 nm) of C3O2 in the presence of excess helium buffer gas and the added reactant gases in a slow flow system, kinetically equivalent to a static system. C(2 3PJ) was then monitored photoelectrically by time-resolved atomic resonance absorption in vacuum UV (λ= 166 nm, 3 3PJâ†� 2 3PJ) with direct computer interfacing for data capture and analysis. The following absolute second-order rate constants for the reactions of C(2 3PJ) with the following alkenes are reported: [graphic omitted] These results, constituting the first reported body of absolute rate data for reactions of ground-state carbon with alkenes, are compared with the analogous body of absolute rate data for atomic silicon in its Si[3p2(3PJ)] ground state, also determined hitherto by time-resolved atomic resonance absorption spectroscopy and demonstrating similar kinetic behaviour. The result for ethene is greater by at least six orders of magnitude than the previous estimate derived from indirect measurements on a flow system and is in accord with earlier considerations of the nature of the potential surface for collision. The result for reaction of C(2 3PJ) with C3O2[kR/cm3 molecule–1 s–1(300 K)=(1.8 ± 0.1)× 10–10] is found to be in accord with earlier measurements.

Investigation of the collisional behaviour of electronically excited germanium atoms, Ge[(4p)2(1D2)], by time-resolved atomic resonance absorption spectroscopy in the ultraviolet

We present a kinetic investigation of the collisional behaviour of the optically metastable, electronically excited germanium atom, Ge[(4p)2(1D2)], 0.883 eV (1 eV ≈ 1.602 18 × 10–19 J) above the (4p)2(3PJ) ground state. The 1D2 atom was generated from the pulsed irradiation (λ≳ 160 nm) of both GeCl4 and Ge(CH3)4 in the presence of an excess of helium gas and the added reactant gases in a slow-flow system, kinetically equivalent to a static system. This was then monitored photoelectrically by time-resolved atomic resonance absorption spectroscopy in the ultraviolet using the resonance transition at λ= 241.737 nm {Ge[(4d)2(1D02)]â†�[(4p)1(1D2)]} and employing direct computer interfacing and signal averaging. Ge(CH3)4 was found to yield the higher densities of the 1D2 state following photolysis and was normally employed as the photochemical precursor with added reactants through GeCl4 could also be used for quenching studies. The following absolute second-order rate constants [kR/cm3 molecule–1 s–1(300 K)] for the removal of Ge(4 1D2) with various collision partners (R) are reported: GeCl4, (2.7 ± 0.1)× 10–10; Ge(CH3)4, (4.2 ± 0.2)× 10–10; H2, (8.3 ± 0.4)× 10–11; D2, (6.9 ± 0.3)× 10–11; Xe, (2.0 ± 0.1)× 10–12; He, <3.6 × 10–16. These results constitute the first reported body of second-order absolute rate data for the collisional removal of Ge(4 1D2), to the best of our knowledge. The resulting rate data are considered in the context of Group 14 atoms in the low-lying (np)2(1D2, 1S0) metastable states in terms of the nature of the potential surfaces involved on collision on the basis of the weak spin–orbit coupling approximation and (J,Ω) coupling and analogous collisional data for Ge[(4p)2(1S0)](E= 2.029 eV) reported hitherto from studies in the ‘single-shot mode’.

The Collisional Quenching of Electronically Excited Germanium Atoms, Ge(4p2(1D2)), with Olefins Studied by Time-Resolved Atomic Resonance Absorption Spectroscopy

Article The Collisional Quenching of Electronically Excited Germanium Atoms, Ge(4p2(1D2)), with Olefins Studied by Time-Resolved Atomic Resonance Absorption Spectroscopy was published on February 1, 1992 in the journal Zeitschrift für Physikalische Chemie (volume 177, issue 2).