Time-resolved Atomic Resonance Fluorescence Research Articles

Reprint of: Quantum yield of chlorine-atom formation in the photodissociation of chlorine peroxide (ClOOCl) at 308 nm

The production of Cl atoms in the laser flash photolysis of ClOOCl at 308nm has been investigated by time-resolved atomic resonance fluorescence at 235K. A value of ϕ=1.03±0.12 has been obtained for the primary quantum yield based on an absorption cross section ratio σ245/σ308=22 for ClOOCl at 245 and 308nm.

Chlorine-Catalyzed Ozone Destruction: Cl Atom Production from ClOOCl Photolysis

Recent laboratory measurements of the absorption cross sections of the ClO dimer, ClOOCl, have called into question the validity of the mechanism that describes the catalytic removal of ozone by chlorine. Here we describe direct measurements of the rate-determining step of that mechanism, the production of Cl atoms from the photolysis of ClOOCl, under laboratory conditions similar to those in the stratosphere. ClOOCl is formed in a cold-temperature flowing system, with production initiated by a microwave discharge of Cl(2) or photolysis of CF(2)Cl(2). Excimer lasers operating at 248, 308, and 352 nm photodissociate ClOOCl, and the Cl atoms produced are detected with time-resolved atomic resonance fluorescence. Cl(2), the primary contaminant, is measured directly for the first time in a ClOOCl cross section experiment. We find the product of the quantum yield of the Cl atom production channel of ClOOCl photolysis and the ClOOCl absorption cross section, (phisigma)(ClOOCl) = 660 +/- 100 at 248 nm, 39.3 +/- 4.9 at 308 nm, and 8.6 +/- 1.2 at 352 nm (units of 10(-20) cm(2) molecule(-1)). The data set includes 468 total cross section measurements over a wide range of experimental conditions, significantly reducing the possibility of a systematic error impacting the results. These new measurements demonstrate that long-wavelength photons (lambda = 352 nm) are absorbed by ClOOCl directly, producing Cl atoms with a probability commensurate with the observed rate of ozone destruction in the atmosphere.

The Kinetics of the Reaction of H Atoms with C4F6

The rate constant k for the gas-phase reaction of atomic hydrogen with 1,1,2,3,4,4-hexafluoro-1,3-butadiene has been measured over the temperature range 290−1010 K by time-resolved atomic resonance fluorescence using H2O and NH3 as precursors, at argon pressures of about 30−140 mbar. Over the range 290−620 K a positive activation energy was observed, k = (3.40 ± 0.34) × 10-11 exp[(−16.7 ± 0.4) kJ mol-1/RT] cm3 molecule-1 s-1, and k dropped rapidly between 620 and 700 K. Over the range 700−1010 K, k = (1.83 ± 0.53) × 10-10 exp[(−34.1 ± 2.1) kJ mol-1/RT] cm3 molecule-1 s-1 where the statistical uncertainties are 1σ. Confidence limits for k are ± 16%. Several isomers of C4F6H were characterized by ab initio methods. Below about 600 K the dominant pathway is suggested to be addition of H atoms to form CF2H−CF•−CFCF2 and/or CF2H−CF•−CFCF2. These adducts dissociate at elevated temperatures, and on the assumption that the major addition product at around 670 K is the more stable CF2H−CF·-CFCF2, the C−H bond diss...

Reaction of O(3P) with ClONO2: Rate Coefficients and Yield of NO3 Product

The rate coefficient for the reaction O(3P) with ClONO2, k1, was measured between 202 and 325 K using two methods: pulsed laser photolysis with time-resolved atomic resonance fluorescence detection of the O atoms and pulsed laser photolysis with long-path tunable diode laser absorption for detection of NO3 radicals. The measured rate coefficient is summarized by k1 = (4.5 ± 1.4) × 10-12 exp[(−900 ± 80)/T] cm3 molecule-1 s-1, with k1(298 K) = (2.2 ± 0.2) × 10-13 cm3 molecule-1 s-1. The yield of NO3 radical in this reaction was measured to be essentially unity. Our results are compared with those from previous studies.

Kinetic studies of the reactions of atomic chlorine and bromine with silane

The kinetics of the reactions Cl( 2 P J )+SiH 4 (1) and Br( 2 P J )+SiH 4 (2) have been investigated by time-resolved atomic resonance fluorescence spectroscopy. Halogen atoms were generated by flash photolysis of CCl 4 and CH 2 Br 2

Formation and decay of (3PJ)O atoms in the laser flash photolysis of chlorine dioxide (OC10) at 308 nm

The quantum yields of O(3P(J)) and Cl(2P(3/2)) atoms released in the laser flash photolysis of OClO at 308 and 298 K were determined and the kinetics of the subsequent oxygen atom decay was investigated using time-resolved atomic resonance fluorescence measurements. The results are consistent with the formation of sym-ClO3 having a Delta Hf(ClO3) (formed in the reaction O + OClO + Ar) of 55.6 +/-4 kcal/mol.

Quantum yield of chlorine-atom formation in the photodissociation of chlorine peroxide (ClOOCl) at 308 nm

The production of Cl atoms in the laser flash photolysis of ClOOCl at 308 nm has been investigated by time-resolved atomic resonance fluorescence at 235 K. A value of φ = 1.03 ± 0.12 has been obtained for the primary quantum yield based on an absorption cross section ratio σ 245/σ 308 = 22 for ClOOCl at 245 and 308 nm.

A high-temperature photochemical kinetics study of the oxygen atom + hydrogen chloride reaction from 350 to 1480 K

Rate coefficients for the O + HCl reaction have been measured by using two differently designed high-temperature photochemistry (HTP) reactors. Measurements were made under pseudo-first-order conditions, (O) {much lt} (HCl), at temperatures from 350 to 1,480 K and pressures from 100 to 613 Torr. Ground-state O atoms were generated by flash photolysis of O{sub 2} or CO{sub 2} and monitored by time-resolved atomic resonance fluorescence with pulse counting. Combining the present data with published measurements in the 350-720 K range yields k(T) = 5.6 {times} 10{sup {minus}21} T{sup 2.87} exp({minus}1,766 K/T)cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} for the 350-1,480 K range with a 2{sigma} confidence interval of 23%, which figure includes a liberal allowance for potential systematic errors.

The tilden lecture. Fundamental collisional processes of alkali and alkaline earth atoms studied by spectroscopic methods

Recent developments for characterising absolute rate data for fundamental reactions of ground-state alkali-metal atoms by direct spectroscopic monitoring in the time-domain are presented against the historical background of diffusion flames. Time-resolved atomic resonance absorption and fluorescence spectroscopy, together with the use of atomic resonance fluorescence techniques in fast-flow systems have led to an extensive body of fundamental rate data that may be compared, in some instances, with measurements derived from molecular beams and some which are of particular relevance to flame chemistry and to the chemistry of alkali-metal atoms in the mesos-phere. Emphasis is given to the kinetic study of the groups of the recombination processes between (i) Li, Na, K, Cs + O2+ M, (ii) Na, K, Rb, Cs + OH + M and (iii), K, Rb, Cs + I + M with detailed consideration of the role of ionic surfaces and the dynamics on those surfaces. Whilst limited consideration is directed towards the study of oxidation reactions of ground state alkaline-earth-metal atoms in diffusion flames and in molecular beams, the kinetic study of electronically excited alkaline-earth-metal atoms which are optically metastable to varying degrees and where collisional removal may compete significantly with radiative loss is dealt with in detail. The general nature of kinetic data for electronically excited alkaline-earth-metal atoms in 3PJ and 1D2 states derived from direct monitoring on low-pressure flames, discharge-flow systems, optical modulation methods and time-resolved emission following pulsed dye-laser excitation is presented. Detailed consideration is principally directed towards the study of diatomic oxidation products in specific vibronic states resulting from collisions between the electronically excited alkaline-earth-metal atoms and simple oxidants using the quantitative combination of time-resolved molecular and atomic emission, on the one hand, and both chemiluminescence and laser-induced fluorescence from molecular beams on the other. The kinetic study of product vibronic states, including the measurements of branching ratios, resulting from direct reaction and energy transfer is described. This quantitative, complementary combination of the time-domain and of the single-collision condition to investigate the details of such product states is emphasised as a major modern development in the study of atomic collisions in specific electronic states.

HTP kinetics studies of the reactions of O(2 3P J) atoms with H2 and D2 over wide temperature ranges

The O+H2(1) and O+D2(2) reactions have been investigated, using the high-temperature photochemistry (HTP) technique, over the 350 to 1420 and 390 to 1420 K temperature ranges, respectively. O(2 3PJ) atoms were generated from flash photolysis of CO2 and monitored by time-resolved atomic resonance fluorescence with pulse counting. Above 430 K the rate coefficients are given by k1(T)=7.3×10−21 (T/K)2.93 exp(−2980 K/T) cm3 molecule−1 s−1 and k2(T)=3.1×10−16 (T/K)1.65 exp (−5260 K/T) cm3 molecule−1 s−1. Combination of our data with those from other experiments which isolated the reactions from secondary processes yields our recommendations k1(T)=1.5×10−12 exp (−3540 K/T)+3.7×10−10 exp (−7450 K/T) cm3 molecule−1 s−1 (300 K≤T≤2500 K) and k2(T)=1.4×10−12 exp(−4260 K/T) +2.9×10−10 exp (−7780 K/T) cm3 molecule−1 s−1 (390 K≤T≤1420 K). Accuracy assessments are discussed in the text. k1(T), k2(T), and the kinetic isotope effect compare well with calculations based on recent ICVT/LAG and CEQB ab initio methods, which suggest that the first terms of the double exponential expressions approximate the tunneling contributions.

High-temperature photochemistry and BAC-MP4 studies of the reaction between ground-state H atoms and N2O

The H+N2O reaction has been investigated using the high-temperature photochemistry (HTP) technique. H(1 2S) atoms were generated by flash photolysis of NH3 and monitored by time-resolved atomic resonance fluorescence with pulse counting. The bimolecular rate coefficient for H-atom consumption, leading essentially to N2+OH, from 390 to 1310 K is found to be given by k1(T)=5.5×10−14 exp(−2380 K/T)+7.3×10−10 exp(−9690 K/T) cm3 molecule−1 s−1; the accuracy is assessed as approximately 25% at the 2σ confidence level. Above 750 K, k1 closely follows the Arrhenius behavior of the second term alone. Distinct curvature is evident below 750 K. k1 is compared to theoretical BAC-MP4 predictions and good agreement is found for a model involving rearrangement of an HNNO intermediate coupled with tunneling through an Eckart potential barrier, which dominates at the lower temperatures. The branching ratio for the channel leading to NH+NO is discussed in the context of recent thermochemical information and a maximum rate coefficient of <1×10−9 exp(−15800 K/T) cm3 molecule−1 s−1 is set for temperatures up to 2000 K.

An HTP kinetics study of the reaction between ground-state H atoms and NH3 from 500 to 1140 K

The H+NH3 reaction has been investigated using the high-temperature photochemistry (HTP) technique. H(1 2S) atoms were generated by flash photolysis of NH3 and monitored by time-resolved atomic resonance fluorescence with pulse counting. The rate coefficient for 660≤T≤1140 K is given by k(T)=(5.7±2.8)×10−10 exp[(−8650±410)K/T] cm3 molecule−1 s−1, where the uncertainties represent one standard deviation based on a propagation of error treatment including systematic errors. The Arrhenius plot reveals curvature between 500 and 660 K which follows the results of quantum mechanical tunneling calculations based on transition state theory and an Eckart potential.

Absolute third-order rate constants for the recombination reactions between alkali-metal and iodine atoms and the measurement for Rb + I + He

We present a direct measurement of the absolute third-order rate constant for the reaction Rb + I + He → RBI + He (1) which is considered within the context of the recombination of alkali-metal atoms and atomic iodine in general. I(5 2P3/2) was generated by the repetitive pulsed irradiation of RbI in a flow system with He, and monitored by time-resolved atomic resonance fluorescence in the vacuum u.v. at λ= 178.3 nm {I[5p4 6s(2P3/2)]–I[5p5(2P3/2)]} using photon counting. Rb(52S1/2) was monitored in the steady mode by atomic resonance fluorescence at λ= 421 nm [Rb(6 2PJ)–Rb(52S1/2)] using phase-sensitive detection. These measurements yield the value of k1(T= 540 K)=(3.34 ± 0.67)× 10–31 cm6 atom–2 s–1. We also report an estimate of the rate constant for the reaction I(5 2P3/2)+ Rb2→ RbI + I (3) of k3(T= 540 K)= 4.1 × 10–10 cm3 molecule–1 s–1, in accord with previous measurements for Br + K2 derived from molecular beams. The recombination reaction was modelled using trajectory calculations with Monte Carlo averaging, coupled with the Landau–Zener formalism for the covalent and ionic surfaces, the latter being constructed using the Rittner potential. The calculated result was in good accord with the experimentally measured result and further employed for extrapolation of k1 to T= 2400 K. Detailed theoretical consideration of the ‘fall-off’ region indicated that the present measurements have been carried out in the region of third-order kinetics. Direct experimental measurements of the recombination between Cs, Rb, K + I + He have now been reported by the present method, together with calculations of these rate constants that are in good accord with experiment. The analogous reactions for the lighter elements, Na and Li, lie beyond the temperature range accessible by the present experimental system, and hence for these we report analogous trajectory calculations only. The overall body of data may be summarised as follows: [graphic omitted] This set of rate constants emphasises the small temperature dependences for all five recombination processes, a direct result of the recombination dynamics occurring on an ionic surface in each case.

Measurement of the absolute third-order rate constant for the reaction between potassium + atomic iodine + helium by time-resolved atomic resonance fluorescence monitoring of iodine atoms in the vacuum ultraviolet (I(5p46s(2P3/2))-I(5p5(2P03/2))) coupled with steady atomic resonance fluorescence on atomic potassium (K(52PJ)-K(42S1/2))

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMeasurement of the absolute third-order rate constant for the reaction between potassium + atomic iodine + helium by time-resolved atomic resonance fluorescence monitoring of iodine atoms in the vacuum ultraviolet (I(5p46s(2P3/2))-I(5p5(2P03/2))) coupled with steady atomic resonance fluorescence on atomic potassium (K(52PJ)-K(42S1/2))John M. C. Plane and David HusainCite this: J. Phys. Chem. 1986, 90, 3, 501–507Publication Date (Print):January 1, 1986Publication History Published online1 May 2002Published inissue 1 January 1986https://doi.org/10.1021/j100275a030RIGHTS & PERMISSIONSArticle Views45Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (850 KB) Get e-Alerts

Measurement of the absolute third-order rate constant for the reaction between Cs + I + He by time-resolved atomic resonance fluorescence monitoring of iodine atoms in the vacuum ultraviolet region {I[6s(2PJ)]–I[5p5(2P3/2)]} coupled with steady atomic resonance fluorescence on atomic caesium [Cs(72PJ)– Cs(62S1/2)] in the visible region

We present a direct kinetic measurement of the absolute third-order rate constant for the reaction Cs + I + He → CsI + He. (1) I(52P3/2) was generated by the repetitive pulsed irradiation of CsI produced in a flow system from the reaction of CH3I in the presence of excess atomic caesium derived from a heat-pipe oven. The ground-state iodine atom was monitored by time-resolved atomic resonance fluorescence at λ= 178.3 nm {I[5p46s(2P3/2)]–I[5p5(2P3/2)]} using photon counting in the vaccum ultraviolet region. Cs(62S1/2) was monitored by steady atomic resonance fluorescence of the Rydberg doublet at λ= 457 nm [Cs(72PJ)–Cs(62S1/2)] using phase-sensitive detection. We report a measured absolute third-order rate constant of k1(T= 491 K)=(7.9 ± 1.2)× 10–31 cm6 atom–2 s–1, which we believe to be the first measurement of its kind. We also report an estimate of the rate constant for the reaction I + Cs2→ CsI + Cs (3) of k3(T= 491 K)≈ 2 × 10–10 cm3 molecule–1 s–1, which is found to be in accord with previous kinetic measurements on I + Na2 and Br + K2. The crossing between the covalent and the ionic surface, described by the Rittner potential function, is found to take place at 17.3 Å, and hence the recombination is governed by the large impact parameters involved on collision. Consideration of the splitting between the two surfaces, coupled with the Landau–Zener formalism and Monte Carlo calculations of trajectories on those surfaces, yields a good quantitative account of the observed kinetic behaviour, not only of the present recombination measurements but also of shock-tube data that have been reported for the dissociation of CsI at elevated temperatures (2400 K). In view of this, despite the clear third-order kinetic behaviour observed here for reaction (1), detailed theoretical consideration of the ‘fall-off’ pressure regime found to satisfy both the present measurements and the shock-tube data leads to the preferred value of k1(T = 491 K)= 9.1 × 10–31 cm6 atom–2 s–1(±25%). The combination of the recombination and dissociation-rate measurements and the modelling calculations lead to the temperature dependence of the form k1(491 < T/K < 2400)= 4.1 × 10–30T–0.24 cm6 atom–2 s–1.

The collisional behaviour of ground state bismuth atoms, Bi(6 4S 0[formula omitted], with alkyl bromides studied by time- resolved atomic resonance fluorescence at λ = 306.77 nm (Bi(7 4P [formula omitted])) following pulsed irradiation: kinetics, radiation trapping and fluorescence quenching of Bi(7 4P [formula omitted

The kinetic study of ground state bismuth atoms, Bi(6 4S 0 3 2 ), has been investigated by time-resolved atomic resonance fluorescence at λ = 306.77 nm (Bi(7 4P 1 2 )-Bi(6 4S 0 3 2 ) in the “single-shot” mode following pulsed irradiation. Bi(6 4S 0 3 2 ) was generated by the flash photolysis of Bi(CH 3) 3 in the presence of excess helium buffer gas and monitored as a function of time with various added bromine-containing molecules as reactants. Absolute second-order rate constants k R Br (cm 3 molecule −1 s −1) ( T = 300 K; errors, 2σ) are reported for the removal of Bi(6 4S 0 3 2 ) by the following molecules: Br 2, (5.3 ± 1.8) × 10 −13; CH 2Br 2, (9.0 ± 1.3) × 10 −15; CH 3Br, (1.8 ± 0.4) × 10 −15; C 2H 5Br, (4.1 ± 0.7) × 10 −15; n-C 3H 7Br, (1.2 ± 0.1) × 10 −14. These results are compared with analogous rate data for the reaction of ground state lead atoms, Pb(6 3P 0). We also present detailed calculations of radiation trapping using various models including the diffusion theory of radiation involving a characteristic mean free path of an emitted photon and a more generalized transport theory for the (Bi(7 4P 1 2 )-Bi(6 4S 0 3 2 )) transition, including the effect of nuclear hyperfine interaction. Consideration is given in the present paper to radiation trapping calculations for atomic densities where the simplifying approximations resulting from the use of “low equivalent opacities” break down. The results of these calculations are presented for various models which lead to relations describing the variation in the effective mean radiative lifetime with atomic density and the functional relationship between fluorescence intensity and particle density.

Kinetic studies of Bi(6 4S [formula omitted]) by time-resolved atomic resonance fluorescence I: Reactions with C 2H 2 (+He), N 2O and fluorescence quenching of Bi(7 4P [formula omitted

We present a kinetic study of ground state atomic bismuth Bi(6 4S 3 2 ) generated by pulsed irradiation of Bi(CH 3) 3 in the presence of various gases and monitored with time-resolved atomic resonance fluorescence in the “single-shot” mode at λ = 306.8 nm (Bi(7 4P 1 2 ) → Bi(6 4S 1 2 ) + hv) following optical excitation. The third-order reaction Bi + C 2H 2 + He is studied in detail, including the effects of diffusion. The resulting third-order rate constant ( k 3 = (1.9 ± 0.3) × 10 −33 cm 6 molecule −2 s −1 (300 K)) is compared with previous data, in particular those from time-resolved resonance absorption measurements. The absolute second-order rate constant for the reaction between Bi(6 4S 3 2 ) and N 2O is also characterized ( k 2 = (2.1 ± 0.4) × 10 −16 cm 3 molecule −1 s −1 (300 K)) and compared with previous upper limits reported for this reaction. Finally, the technique is applied to the study of fluorescence quenching of Bi(7 4P 1 2 ) for which we report the following quenching cross sections σ 2 (Å 2) (errors, about 25%): N 2, 3.8; NO, 169; O 2, 570; N 2O, 164; CF 4, 12; C 2H 2, 97. These data are compared, where possible, with measurements of quenching cross sections derived from Stern—Volmer analyses on integrated plate intensities resulting from atomic emission following flash photolysis. The results from the two fundamentally different techniques are found to be in reasonable accord.

Kinetic studies of Bi(6 4S [formula omitted]) by time-resolved atomic resonance fluorescence II: An investigation of the third-order reactions Bi + O 2 + M and Bi + NO + M (M  He, N 2 and CF 4)

Kinetic studies of the removal of ground state bismuth atoms Bi(6 4S 3 2 ) with O 2 and NO are reported following measurements of time-resolved atomic resonance fluorescence at λ = 306.8 nm (Bi(7 4P 1 2 ) → Bi(6 4S 3 2 ) + hv) subsequent to the flash photolysis of Bi(CH 3) 3. These processes were investigated in the presence of the buffer gases He, N 2 and CF 4 where significant diffusional corrections were found necessary with the resonance fluorescence technique for the pressure ranges employed with these gases. Overall third-order kinetics were observed for both Bi + O 2 + M and Bi + NO + M (M  He, N 2 and CF 4) yielding the following absolute third-order rate constants k 3 (cm 6 molecule −2 s −1) (300 K; errors, 2σ): k 3(Bi + O 2 + He) = (3.3 ± 0.3) × 10 −32; k 3(Bi + O 2 + N 2) = (8.9 ± 0.9) × 10 −32; k 3(Bi + O 2 + CF 4) = (1.3 ± 0.4) × 10 −31; k 3(Bi + NO + He) = (3.9 ± 0.4) × 10 −33; k 3(Bi + NO + N 2) = (1.3 ± 0.2) × 10 −32; k 3(Bi + NO + CF 4) = (2.7 ± 0.8) × 10 −32. These data are compared, where possible, with results derived from resonance absorption measurements on Bi(6 4S 3 2 ) and also with analogous processes for the atomic states Sb(5 4S 3 2 ), Pb(6 3P 0) and Sn(5 3P 0).

Determination of the rate constant of reaction of ground-state CI and H atoms with H 2S using resonance fluorescence in a discharge flow

Rate constants k (1α) (cm 3 molecule −1 s −1) for Cl + H 2S → HCl + Hs, k 1 = (4.00 ± 0.08) × 10 −11; and H + H 2S → H 2 + HS, k 2 = (7.41 ± 0.39) × 10 −13, have been measured using a resonance fluorescence technique in a discharge flow system. k 2 is in agreement with previous values derived from time-resolved atomic resonance fluorescence following flash photolysis and from EPR measurements on a flow discharge system. k 1 is smaller than the value obtained from time-resolved infrared chemiluminescence measurements on vibrationally excited HCl following laser photolysis of S 2Cl 2. The role of secondary reactions arising from measurements made at high atomic concentrations is investigated experimentally.

Kinetic study of Ca(43PJ) by time-resolved emission, 43P1→ 41S0+hν(λ= 657.3 nm), following dye-laser excitation. Spontaneous emission, diffusion and collisional quenching

We present a kinetic study of the low-lying electronically excited state of atomic calcium, Ca[4s4p(3PJ)], 1.885 eV above the 4s2(1S0) ground state. Ca(4 3P1) was generated by dye-laser pulsed excitation at λ= 657.3 nm of calcium vapour [Ca(4 3P1)â†� Ca(4 1S0)] at elevated temperatures (1000 K), in equilibrium with solid calcium, in a slow-flow system, kinetically equivalent to a static system. Following rapid Boltzmann equilibration within Ca(4 3PJ) through collisions, the forbidden time-resolved atomic resonance fluorescence at the same wavelength was monitored using boxcar integration. The decay of Ca(4 3PJ) in the presence of all the noble gases, He, Ne, Ar, Kr and Xe, was studied, yielding measurements of relative diffusion coefficients. Extrapolation of the diffusional component of the decay in each noble gas to infinite pressure yields an independent value of the mean radiative lifetime for Ca(4 3P1)→ Ca(4 1S0)+hν(λ= 657.3 nm), the average of which from the measurements in all the noble gases yields τe= 0.34 ± 0.02 ms (error 2σ). This result is compared with values reported from previous measurements, particularly atomic beams and time-resolved measurements. The kinetic analysis also gives rise to data for the collisional quenching of Ca(4 3PJ), which is found to be insignificant for most of the noble gases [kHe,Ne,Ar,Kr⩽ 4 × 10–15 cm3 molecule–1 s–1(1000 K)], in contrast to measurements from earlier work using phase-shift techniques. Xenon, however, exhibited measurable rates of collisional quenching of Ca(4 3PJ) characterised by kXe= 2.4 ± 0.3 × 10–14 cm3 molecule–1 s–1(1000 K). The time-resolved emission technique is further applied to the study of the removal of Ca(4 3PJ) by added gases, for which we report (errors 1σ)kN2=(8.9 ± 0.9)× 10–13 cm3 molecule–1 s–1(1000 K), kH2=(6.0 ± 0.6)× 10–14 cm3 molecule–1 s–1(1000 K), kD2=(2.7 ± 0.3)× 10–14 cm3 molecule–1 s–1(1000 K).