Kinetic investigation of the time-resolved atomic fluorescence Ca(43P1→ 41S0) and molecular chemiluminescence CaCl(A2Π, B2Σ+→ X2Σ+) following the pulsed dye-laser generation of Ca(43PJ) in the presence of CH3Cl

Beitia, Fernando; Castaño, Fernando; Rayo, M. N. Sanchez; Carl, Shaun A.; Husain, D.; Santos, L.

doi:10.1039/ft9918702413

Cited by 13 publications

(14 citation statements)

References 46 publications

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“…In contrast to previous measurements on Ca(4 3 P J ) + CH 3 X in the timedomain [16][17][18][19], the present system requires a combination of the comparisons of time-dependences for atomic and molecular emissions together with determinations of integrated intensities using an optically calibrated system [20,21,[23][24][25][26][27]. Ca[4s4 p( 3 P 1 )] was generated by the pulsed dye-laser excitation (10 Hz) of calcium vapour at elevated temperature (T = 940 K) at λ = 657.3 nm {Ca[4s4 p( 3 P 1 )] ← Ca[4s 2 ( 1 S 0 )]} in the presence of methyl bromide and excess helium buffer gas in a slow flow system, kinetically equivalent to a static system.…”

Section: Methodscontrasting

confidence: 83%

“…Ca[4s4 p( 3 P 1 )] was generated by the pulsed dye-laser excitation (10 Hz) of calcium vapour at elevated temperature (T = 940 K) at λ = 657.3 nm {Ca[4s4 p( 3 P 1 )] ← Ca[4s 2 ( 1 S 0 )]} in the presence of methyl bromide and excess helium buffer gas in a slow flow system, kinetically equivalent to a static system. The materials (Ca, 99%; He, 99.999%; CH 3 Br Aldrich) were employed essentially as described in previous investigations [17]. Molecular chemiluminescence from the states CaBr(A 2 Π 1/2,3/2 , B 2 Σ + → X 2 Σ + ) were also monitored.…”

Section: Methodsmentioning

confidence: 99%

“…The gain (G) for the photomultiplier tube (E.M.I., 9797B) as a function of voltage was taken from the commercial calibration expressed in the form ln(G/arb.units) = 8.7 ln(V/Volts) − 54.4 [30]. In contrast to the previous time-resolved investigation on Ca( 3 P J ) + CH 3 Br [18] using the largest pair of slits (600 µm) for the monochromator [17], a smaller pair of slits (300 µm) were employed in these measurements in order to increase the wavelength resolution for the recorded molecular chemiluminescence profiles, particularly for the two close-lying spin-orbit components of CaBr(A 2 Π 1/2,3/2 -X 2 Σ + ) at 627.8 and 625.3 nm, respectively (see later). This yielded two peaks in the sensitivity response curve, one at ca.…”

Section: Methodsmentioning

confidence: 99%

“…where A nm = 1/τ e for Ca( 3 P 1 -1 S 0 ) and F = (1 + 1/K 1 + K 2 ) [16][17][18][19]. A nm has been characterised separately in this work from measurements of atomic decay profiles similar to that in Fig.…”

Section: Time-dependence Of the Atomic Emission Ca[4s4 P(mentioning

confidence: 99%

“…CaX(A 2 Π 1/2,3/2 , B 2 Σ + ) have been shown to result from direct reaction in studies of the time-resolved atomic fluorescence and molecular chemiluminescence following the collisions of Ca(4 3 P J ) + CH 3 X (X = F, Cl, Br, I) [16][17][18][19]. Those measurements may be contrasted to analogous later investigations in the time-domain on the reactions Sr(5 3 P J ) [23][24][25][26][27], 1.807 eV above the 5s 2 ( 1 S 0 ) ground state, following pulsed dye-laser excitation of atomic strontium in the presence of various halides which did yield molecular electronic product branching ratios.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Husain¹,

Geng²,

Castaño³

et al. 2001

Zeitschrift Für Physikalische Chemie

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Molecular electronic branching ratios to yield CaBr(A 2 Π 1/2 ), CaBr(A 2 Π 3/2 ) and CaBr(B 2 Σ + ) have been determined in the time-domain following the reaction of Ca[4s4 p( 3 P J )], 1.888 eV above the 4s 2 ( 1 S 0 ) ground state, with CH 3 Br. Ca[4s4 p( 3 P 1 )] was generated by the pulsed dye-laser excitation of ground state calcium atoms at λ = 657.3 nm {Ca[4s4 p( 3 P 1 )] ← Ca[4s 2 ( 1 S 0 )]} at elevated temperatures in the presence of CH 3 Br and excess helium buffer gas. Measurements were then made of the atomic resonance fluorescence from Ca(4 3 P 1 → 4 1 S 0 ) and the molecular chemiluminescence from CaBr(A 2 Π 1/2 , A 2 Π 3/2 , B 2 Σ + → X 2 Σ + ) after Boltzmann equilibration with Ca(4 3 P 0,1,2 ). The following molecular chemiluminescence emissions were recorded: CaBr(A 2 Π 1/2 → X 2 Σ + , ∆v = 0, λ = 628 nm), CaBr(A 2 Π 3/2 → X 2 Σ + , ∆v = 0, λ = 625 nm) and CaBr(B 2 Σ + → X 2 Σ + , ∆v = 0, λ = 611 nm). The atomic and molecular emissions demonstrated exponential decays characterised by decay coefficients which were equal under identical chemical conditions thus demonstrating the production of CaBr(A 2 Π 1/2,3/2 , B 2 Σ + ) by direct reaction of Ca( 3 P J ) with CH 3 Br. The combination of the time-dependences of the atomic and molecular profiles together with the integrated atomic and molecular intensities, placed on a common intensity scale by calibration of the optical system against a spectral radiometer, yielded branching ratios into the A 2 Π 1/2 , A 2 Π 3/2 and B 2 Σ + states of CaBr. These were found to be as follows: A 1/2 (9.8 ± 3.0) · 10 −4 ; A 3/2 (8.5 ± 3.4) · 10 −4 and B, (3.4 ± 1.7) · 10 −4 . To the best of our knowledge, these data represent the first measurements of electronic branching ratios of calcium bromide into specific molecular states for reactions of Ca(4 3 P J ). The results are compared with various related data for total branching ratios into electronic states studied in the single collision condition for this atomic state with CH 3 Br using molecular beams, and with analogous measurements for Ca(4 3 P J ) + CH 3 F and CH 3 Cl. These results are also compared with branching ratios of SrBr(A 2 Π 1/2 , A 2 Π 3/2 , B 2 Σ + ) following the reaction of Sr[5s5 p( 3 P J )] + CH 2 Br 2 investigated following pulsed dye-laser generation of Sr(5 3 P J ).

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Section: Methodscontrasting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Time-dependence Of the Atomic Emission Ca[4s4 P(mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Husain¹,

Geng²,

Castaño³

et al. 2001

Zeitschrift Für Physikalische Chemie

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Kinetic Investigation of the Time‐Resolved Atomic Fluorescence Ca(4³P₁ → 4¹S₀) and Molecular Chemiluminescence CaI(A²Π, B²Σ⁺ → X²Σ⁺) Following the Pulse‐Dye Laser Generation of Ca(4³P_J) in the Presence of CH₃I

Basterrechea

Beitia

Castaño

et al. 1991

Ber Bunsenges Phys Chem

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The collisional behaviour of the optically metastable, electronically excited calcium atom, Ca(4s4p(3P1)), 1.888 eV above its 4s2(1S0) electronic ground state, is investigated in the time‐resolved mode following its generation by pulsed dye‐laser excitation at elevated temperature from calcium vapour in the presence of CH3I and excess helium buffer gas in a slow flow system, kinetically equivalent to a static system. The removal of Ca(43P1) is monitored by time‐resolved atomic fluorescence at the resonance wavelength ( λ = 657.3 nm, Ca(43P1) → Ca(41S0) + hv), following rapid Boltzmann equilibration within the 43P1 spin‐orbit manifold using boxcar integration. Electronically excited CaI in the A2Π and B2Σ+ states, respectively 1.9372 (186.9 kJ mol−1) and 1.9466 eV (187.8 kJ mol−1) above the X2Σ+ ground state, was also monitored by time‐resolved molecular chemiluminescence of the A, BX systems under identical conditions to those employed for characterising the decay profiles of Ca(43P1). Both atomic and molecular chemiluminescence emissions showed exponential decay profiles, characterised by first‐order decay coefficients which were found to be equal under the same experimental conditions. CaI(A2II) and CaI(B2Σ+) are thus shown to arise from direct production on the collision of Ca(43P1) with CH3I where these processes are energetically favourable: As with complementary measurements that have been reported on the collisional behaviour of Ca(43PJ) with CH3I under single‐collision conditions in molecular beams, where the AX and BX chemiluminescence of CaI was recorded, it was not possible to resolve the AX and BX profiles individually in view of spectroscopic overlap between these two close lying electronic states where vibrational population in higher levels of the A and B states at these elevated temperatures (900 K) also complicates the chemiluminescence spectra, as well as the spin‐orbit components in CaI(A2II1/2, 3/2). Time‐resolved chemiluminescence from CaI(A, BX) is hence employed the to monitor the global emission from these two electronically excited states. Thus, the A, BX emission can be used as an overall spectroscopic marker for Ca(43PJ) in the time‐domain and can be used to estimate a reaction rate constant for the overall collisional removal of Ca(43PJ) by CH3I of ca. 2 · 10−11 cm3 molecule−1 s−1 at T = 900 K though this must be viewed with caution on account of reaction of ground state Ca(41S0) with CH3I in the flow system prior to dye laser excitation. Broad band chemiluminescence is recorded for the Ca(43P1)CH3I system as well as laser‐induced fluorescence by excitation of the X2Σ+ state which is also generated on reaction of the excited atom. The principal conclusion of the present investigation in the time‐domain is the direct production of CaI(A2Π, B2Σ+) on the collision of Ca(43P1) with CH3I, in accord with complementary observations that have been made hitherto under single‐collision conditions and which are compared with the present investigation. The present results for ...

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Electronic Energy Distribution in SrF by Investigation of the Molecular Chemiluminescence SrF(A²II_1/2,3,2B²Σ⁺ → X²Σ⁺) and the Atomic Resonance Fluorescence Sr(5³P₁‐5¹S₀) in the Time‐Domain following the Pulsed Dye Laser Generation of Sr(5³P_J) in the presence of CH₃F

Antrobus

Carl

Husain

et al. 1995

Ber Bunsenges Phys Chem

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A kinetic study is presented of the electronic energy distribution in SrF following the reaction of the electronically excited strontium atom, Sr (5s5p('P ,)), 1.807 eV above its 5s2('S0) electronic ground state, with CH,F. This optically metastable atom was generated by pulsed dye-laser excitation of ground state strontium vapour to the Sr(53P,) state at J. = 689.3 nm (Sr(53P,+5fS,)) at elevated temperature (850 K) in the presence of excess helium buffer gas in a slow flow system, kinetically equivalent to a static system. The decay of Sr(5'P,,) was then monitored by time-resolved atomic fluorescence from Sr (53P,) at the resonance wavelength following rapid Boltzmann equilibration within the 3PJ spin-orbit manifold. Electronically excited SrF resulting from reaction of the excited atom with CH3F was also recorded in the time-domain via the systems SrF(A2III,,+XZZ+) ( A u = O , I = 6 6 2 n m ) , SrF(A2113,2+X2Zt) ( A u = O , J.=652nm) and SrF(B2Z+-X2Ct) ( A u = O , /I = 579 nm). The A 2 n (181.9 kJ mol-I) and B2Z + (206.6 kJ mol-I) states of SrF are both energetically accessible on collision between Sr('P) and CH,F. Both the atomic and molecular (A,B-X) chemiluminescence emissions are shown to be exponential in form and characterised by first-order decay coefficients which are found to be equal under identical conditions within experimental error. SrF(A2n) and SrF(B2Z ' ) are thus both shown to arise from direct reaction with CH,F. Further, the combination of integrated atomic and molecular intensity measurements, coupled with optical sensitivity calibration, enables estimates of the branching ratios into the A,,,, ,*, B and X states arising from Sr(5'PJ)+CH3F to be made yielding the following results: A,,,, 6 . 4~ lo-'; A,,,, 1 . 5~1 0 --~; B, 1.1 x X, 0.992. The results obtained here are compared with analogous chemiluminescence studies on Sr (3P) with other halides obtained from molecular beam measurements and with previous kinetic measurements on SrC1, Br(A2n, B2X+ -X 2 Z + ) that we have reported. The results are also compared with those from a series of investigations we have presented from time-domain investigations of molecular emissions from CaF, Cl, Br, I (A,B-X) arising from the collisions of Ca(43P,) with appropriate halides.

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Kinetic investigation of the time-resolved atomic fluorescence Ca(4³P₁→ 4¹S₀) and molecular chemiluminescence CaCl(A²Π, B²Σ⁺→ X²Σ⁺) following the pulsed dye-laser generation of Ca(4³P_J) in the presence of CH₃Cl

Cited by 13 publications

References 46 publications

Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Kinetic Investigation of the Time‐Resolved Atomic Fluorescence Ca(4³P₁ → 4¹S₀) and Molecular Chemiluminescence CaI(A²Π, B²Σ⁺ → X²Σ⁺) Following the Pulse‐Dye Laser Generation of Ca(4³P_J) in the Presence of CH₃I

Electronic Energy Distribution in SrF by Investigation of the Molecular Chemiluminescence SrF(A²II_1/2,3,2B²Σ⁺ → X²Σ⁺) and the Atomic Resonance Fluorescence Sr(5³P₁‐5¹S₀) in the Time‐Domain following the Pulsed Dye Laser Generation of Sr(5³P_J) in the presence of CH₃F

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Kinetic investigation of the time-resolved atomic fluorescence Ca(43P1→ 41S0) and molecular chemiluminescence CaCl(A2Π, B2Σ+→ X2Σ+) following the pulsed dye-laser generation of Ca(43PJ) in the presence of CH3Cl

Cited by 13 publications

References 46 publications

Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Determination of the Branching Ratios of CaBr(A2Π1/2,3/2, B2Σ+) Resulting from the Reaction of Ca[4s4p (3PJ)] with CH3Br by Time-Resolved Atomic Emission and Molecular Chemiluminescence Following Pulsed Dye-Laser Excitation of Atomic Calcium

Kinetic Investigation of the Time‐Resolved Atomic Fluorescence Ca(43P1 → 41S0) and Molecular Chemiluminescence CaI(A2Π, B2Σ+ → X2Σ+) Following the Pulse‐Dye Laser Generation of Ca(43PJ) in the Presence of CH3I

Electronic Energy Distribution in SrF by Investigation of the Molecular Chemiluminescence SrF(A2II1/2,3,2B2Σ+ → X2Σ+) and the Atomic Resonance Fluorescence Sr(53P1‐51S0) in the Time‐Domain following the Pulsed Dye Laser Generation of Sr(53PJ) in the presence of CH3F

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Kinetic investigation of the time-resolved atomic fluorescence Ca(4³P₁→ 4¹S₀) and molecular chemiluminescence CaCl(A²Π, B²Σ⁺→ X²Σ⁺) following the pulsed dye-laser generation of Ca(4³P_J) in the presence of CH₃Cl

Kinetic Investigation of the Time‐Resolved Atomic Fluorescence Ca(4³P₁ → 4¹S₀) and Molecular Chemiluminescence CaI(A²Π, B²Σ⁺ → X²Σ⁺) Following the Pulse‐Dye Laser Generation of Ca(4³P_J) in the Presence of CH₃I

Electronic Energy Distribution in SrF by Investigation of the Molecular Chemiluminescence SrF(A²II_1/2,3,2B²Σ⁺ → X²Σ⁺) and the Atomic Resonance Fluorescence Sr(5³P₁‐5¹S₀) in the Time‐Domain following the Pulsed Dye Laser Generation of Sr(5³P_J) in the presence of CH₃F