Measurement of the Natural Lifetimes and Quenching Rate Constants of OH(2Σ+, v = 0,1) and OD(2Σ+, v = 0,1) Radicals

1973 ◽  
Vol 28 (2) ◽  
pp. 249-256 ◽  
Author(s):  
K. H. Becker ◽  
D. Haaks
Keyword(s):  
Rate Constants ◽  
Fluorescence Decay ◽  
Quenching Rate ◽  
Pulse Photolysis ◽  
Electronic Interactions ◽  
Electronically Excited ◽  
Vacuum Uv

The lifetimes of OH(2Σ+) and OD(2Σ+) radicals were measured by using pulse-photolysis of water and methanol in the vacuum-uv for the production of the electronically excited radicals. From the fluorescence decay measurements the natural lifetimes, as well as the quenching rate constants for several added gases such as H2O, CH3OH, H2, N2, Ar, and He were determined. In particular, the natural lifetime of OH (2Σ+, v = 0), τ = (1.00 ± 0.06) · 10-6 s, was corrected for rotation-vibration as well as for rotation-electronic interactions resulting in a lifetime of (0.83 ± 0.08) · 10-6 s for the rotationless state. A lifetime of (0.82 ± 0.08) · 10-6 s was derived for the rotationless state of OD(2Σ+,v = 0).

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

scholarly journals Measurements of rate constants of O2(b) quenching by CH4, NO, N2O at temperatures 300-800 K

2018 ◽  
Vol 209 ◽  
pp. 00006
Author(s):  
G.I. Tolstov ◽  
M.V. Zagidullin ◽  
N.A. Khvatov ◽  
I.A. Medvedkov ◽  
A.M. Mebel ◽  
...  
Keyword(s):  
Rate Constants ◽  
Room Temperature ◽  
Quenching Rate ◽  
Important Place ◽  
The Past ◽  
Tunable Dye Laser ◽  
Deactivation Kinetics ◽  
Electronically Excited ◽  
Excited Oxygen ◽  
Good Agreement

Electronically excited oxygen has an important place in the kinetic schemes of the processes taking place in the atmosphere, in the active medium of an oxygen-iodine laser, and in plasma-assisted combustion1. Over the past decades, a large amount of data on the rate constants of quenching O2(b) on a large number of collision partners has been accumulated. However, they mostly refer to the results of measurements at room temperature. In this paper, rate constants for the quenching of O2(b) by collisions with N2O, NO, and CH4 have been determined in the temperature range from 297 to 800 K, by the laser-induced fluorescence method. O2(b) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed via observing the temporal behavior of the b1Σg+→ X3Σg- fluorescence. From the analysis of experimental results, the following temperature dependencies of the quenching rate constants by these gases were obtained, and could be represented by the expressions: kNO=(1.77±0.2)×10-24×T3.5 exp(1138±37/T); kN2O=(2.63±0.14)×10-16×T1.5×exp(590±26/T) and kCH4=(3.54±0.4)×10-18×T1.5×exp(-220±24/T) cm3s-1. All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.

Quenching of Fluorescence of Chloropentafluoroacetone by Saturated Hydrocarbons

1972 ◽  
Vol 50 (9) ◽  
pp. 1429-1432 ◽  
Author(s):  
A. J. Yarwood
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Singlet State ◽  
Fluorescence Yield ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Quenching Rate ◽  
Saturated Hydrocarbons ◽  
Phase Measurements ◽  
Electronically Excited

Saturated hydrocarbons can quench the electronically excited singlet state of a simple ketone in the gas phase. Measurements on the quenching of the fluorescence yield of chloropentafluoroacetone at 23 °C show that different saturated hydrocarbons can deactivate the excited singlet state with varying efficiencies. The quenching rate constants are reported and possible relationships considered.

Fluorescence Lifetime and Quenching Rates for N,N,N′,N′-Tetramethyl-P-Phenylenediamine in the Vapor Phase

1989 ◽  
Vol 43 (8) ◽  
pp. 1406-1409 ◽  
Author(s):  
S. K. Nickle ◽  
L. A. Melton
Keyword(s):  
Vapor Phase ◽  
Fluorescence Lifetime ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Rate ◽  
Electronically Excited ◽  
Visualization Systems ◽  
Fuel Evaporation ◽  
Vapor Liquid

The fluorescence lifetime of N,N,N′,N′-tetramethyl- p-phenyIenediamine (TMPD) in the vapor phase has been determined to be 3.2 ± 0.3 ns for excitation at 337 nm. The rate constants for quenching of electronically excited TMPD by ground-state TMPD, O2, and CO2 have been determined to be <1 × 10−10 cm3/s, (9.9 ± 1.0) × 10−10 cm3/s, and <4 × 10−13 cm3/s, respectively. The rate for TMPD implies that self-quenching is negligible up to pressures of at least 10 Torr. The quenching rate by oxygen is sufficiently high to ensure that use of TMPD as a quantitative marker for fuel evaporation in exciplex-based vapor/liquid visualization systems is probably not possible if significant quantities of oxygen—as would be the case in combustion environments—are present.

Quenching rate constants for reactions of Ar(4p′[1/2]0, 4p[1/2]0, 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases

2001 ◽  
Vol 115 (7) ◽  
pp. 3144-3154 ◽  
Author(s):  
N. Sadeghi ◽  
D. W. Setser ◽  
A. Francis ◽  
U. Czarnetzki ◽  
H. F. Döbele
Keyword(s):  
Rate Constants ◽  
Quenching Rate

INTERSYSTEM CROSSING OF THE ELECTRONICALLY EXCITED DIDEUTEROETHYLENE MOLECULES FORMED IN BENZENE PHOTOSENSITIZATION

1966 ◽  
Vol 44 (18) ◽  
pp. 2173-2180 ◽  
Author(s):  
Terumi Terao ◽  
Shun-Ichi Hirokami ◽  
Shin Sato ◽  
R. J. Cvetanović
Keyword(s):  
Excited State ◽  
Experimental Evidence ◽  
Rate Constants ◽  
Intersystem Crossing ◽  
Molecular Decomposition ◽  
Electronically Excited

Experimental evidence is presented for a rapidly occurring intersystem crossing of the electronically excited dideuteroethylene molecules initially formed in the benzene-photosensitized reaction at 2 537 Å and 25 °C to another excited state which is responsible for the internal H-atom scrambling. The mechanism is entirely analogous to that previously postulated for the photoexcited states sensitized by Hg(3P1) atoms but the rate constants for intersystem crossing and molecular decomposition are drastically decreased as a result of the smaller amount of energy available for the excitation.

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

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