Isotope effects in the quenching of electronically excited atoms. Quenching of I(52P½) by methane and deuteromethanes studied by time-resolved resonance fluorescence

1979 ◽  
Vol 75 (0) ◽  
pp. 1557-1564 ◽  
Author(s):  
Robert J. Donovan ◽  
Harold M. Gillespie ◽  
William H. Breckenridge ◽  
Constantine Fotakis
Keyword(s):  
Isotope Effects ◽  
Resonance Fluorescence ◽  
Time Resolved ◽  
Excited Atoms ◽  
Electronically Excited

The collisional quenching of electronically excited oxygen atoms, O(21D2), by the gases NH3, H2O2, C2H6, C3H8, and C(CH3)4, using time-resolved attenuation of atomic resonance radiation

1976 ◽  
Vol 54 (11) ◽  
pp. 1765-1770 ◽  
Author(s):  
I. S. Fletcher ◽  
D. Husain
Keyword(s):  
Resonance Radiation ◽  
Recent Measurement ◽  
Absolute Rate ◽  
Collisional Quenching ◽  
Time Resolved ◽  
Excited Atoms ◽  
Electronically Excited ◽  
Hartley Band ◽  
Excited Oxygen ◽  
Oxygen Atoms

A kinetic study of electronically excited oxygen atoms, O(21D2), is presented. These optically metastable species were generated by repetitive pulsed irradiation in the Hartley-band continuum and monitored photoelectrically in absorption by time-resolved attenuation of resonance radiation at λ = 115.2 nm (O(31D20)←O(21D2). Absolute rate constants for the collisional quenching of O(21D2) are reported for the gases NH3, H2O2, C2H6 C3H8, and C(CH3)4. These are found to be respectively (in units of 10−10 cm3 molecule−1 S−1 at 300 K), 6.3 ± 0.7, 5.2 ± 0.6, 7.3 ± 0.8, 9.5 ± 1.0, and 12.3 ± 1.3. With the exception of a recent measurement for NH3• these data represent the first absolute measurements for these quenching gases. Further, a general comparison is made between absolute rate measurements using this technique and recent work by Schiff and co-workers using time-resolved emission at λ = 630 nm (O(21D2) → O(23P2)) in order to monitor the excited atoms.

scholarly journals Time-Resolved Investigation of the Molecular Chemiluminescence SrI(A2∏1/2,3,2,B2∑+→X2∑+) and the Atomic Resonance Fluorescence Sr(53P1→51S0) Following The Pulsed Dye Laser Generation Of Sr(53PJ) in the Presence of CF3I

1995 ◽  
Vol 16 (2) ◽  
pp. 121-138 ◽  
Author(s):  
S. Antrobus ◽  
D. Husain ◽  
Jie Lei ◽  
F. Castaño ◽  
M. N. Sanchez Rayo
Keyword(s):  
Ground State ◽  
Branching Ratio ◽  
Atomic Emission ◽  
Electronic Energy ◽  
Dye Laser ◽  
Pulsed Dye Laser ◽  
Laser Generation ◽  
Buffer Gas ◽  
Resonance Fluorescence ◽  
Time Resolved

A time-resolved investigation is presented of the electronic energy distribution in SrI following the collision of the optically metastable strontium atom, Sr [5s5p(3PJ)], with the molecule CF3I. Sr[5s5p(3PJ)], 1.807 eV above its 5s2(1S0) electronic ground state, was generated by pulsed dye-laser excitation of ground state strontium vapour to the Sr(53P1) state at , λ =689.3 nm {Sr(53P1←51S0)} at elevated temperature (840 K) in the presence of excess helium buffer gas in which rapid Boltzmann equilibration within the 53PJ spin-orbit manifold takes place. Time resolved atomic emission from Sr(53P1→51S0) at the resonance transition and the molecular chemiluminescence from SrI(A2∏1,2,3/2,B2∑+→X2∑+) resulting from reaction of the excited atom with CF3I were recorded and shown to be exponential in character. SrI in the A2∏1/2,3/2 (172.5, 175.4 kJ mol-1) and B2∑+ (177.3 kJ mol-1) states are energetically accessible on collision by direct-I-atomic abstraction between Sr(3P) and CF3I. The first-order decay coefficients for the atomic and molecular emissions are found to be equal under identical conditions and hence SrI(A2∏1/2,3/2, B2∑+) are shown to arise from direct I- atom abstraction reactions. The molecular systems recorded were SrI (A2∏1/2→X2∑+, Δv=0, λ=694 nm), SrI(A2∏3/2→X2∑+, Δv=0, λ=677 nm) and SrI(B2∑+→X2∑+) (Δv=0, λ=674 nm), dominated by the Δv=0 sequences on account of Franck-Condon considerations. The combination of integrated m61ecular and atomic intensity measurements yields estimates of the branching ratios into the specific electronic states, A1/2, A3/2 and B, arising from Sr(53PJ)+CF3I which are found to be as follows: A1/2,1.2 × 10-2; A3/2, 6.7 × 10-3; B, 5.1 × 10-3 yielding ∑SrI(A1/2+A3/2+B)=2.4 × 10-2. As only the X, A and B states SrI are accessible on reaction, assuming that the removal of Sr(53PJ) occurs totally by chemical removal, this yields an upper limit for the branching ratio into the ground state of ca. 98%. The present results are compared with previous time-resolved measurements on excited states of strontium halides that we have reported on various halogenated species resulting from reactions of Sr(53PJ), together with analogous chemiluminescence studies on Sr(3PJ) and Ca(43PJ) from molecular beam measurements.

Recent advances in the chemistry of electronically excited atoms

1970 ◽  
Vol 70 (4) ◽  
pp. 489-516 ◽  
Author(s):  
Robert J. Donovan ◽  
David. Husain
Keyword(s):  
Excited Atoms ◽  
Recent Advances ◽  
Electronically Excited
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