Infrared molecular lasers pumped by electronic-vibrational energy transfer from Br(42<i>P</i>1/2): CO2, N2O, HCN, and C2H2

Petersen, Alan B.; Wittig, C.; Leone, Stephen R.

doi:10.1063/1.88456

Cited by 72 publications

(9 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…18 Photodissociation of Cl 2 at 355 nm is known to produce >99% of the chlorine atoms in the 2 P 3/2 ground state. 19,20 The three fine structure levels of O( 3 P J ) are sufficiently closely spaced in energy that it is safe to assume rapid equilibration via collisions with the N 2 buffer gas.…”

Section: Experimental Techniquementioning

confidence: 99%

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

2000

View full text Add to dashboard Cite

A laser flash photolysis-resonance fluorescence technique has been employed to investigate the kinetics of reactions of the important stratospheric species bromine nitrate (BrONO 2 ) with ground-state atomic bromine (k 1 ), chlorine (k 2 ), and oxygen (k 3 ) as a function of temperature (224-352 K) and pressure (16-250 Torr of N 2 ). The rate coefficients for all three reactions are found to be independent of pressure and to increase with decreasing temperature. The following Arrhenius expressions adequately describe the observed temperature dependencies (units are 10 -11 cm 3 molecule -1 s -1 ): k 1 ) 1.78 exp(365/T), k 2 ) 6.28 exp(215/T), and k 3 ) 1.91 exp(215/T). The accuracy of reported rate coefficients is estimated to be 15-25% depending on the magnitude of the rate coefficient and on the temperature. Reaction with atomic oxygen is an important stratospheric loss process for bromine nitrate at altitudes above ∼25 km; this reaction should be included in models of stratospheric chemistry if bromine partitioning is to be correctly simulated in the 25-35 km altitude regime.

show abstract

Section: Experimental Techniquementioning

confidence: 99%

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

2000

View full text Add to dashboard Cite

show abstract

“…18 Despite this long history, no photochemical or thermal reactivity between Br 2 and CO 2 has previously been noted. This is likely because their photoreaction rate to form a metastable adduct depends supralinearly on both photon and CO 2 concentrations.…”

Section: ■ Discussionmentioning

confidence: 98%

Bromine-Sensitized Solar Photolysis of CO₂

2012

View full text Add to dashboard Cite

Direct photochemical reduction of CO(2) has generally been accomplished by using transition-metal compounds as electron transfer reagents. Here, we show that elemental bromine can function as an alternative photosensitizer. When sunlight is tightly focused on mixtures of CO(2) and Br(2), in the presence of a polar adsorbent such as silica gel, glass wool, alumina, or titania, a metastable red adduct is formed within seconds and concentrates at the point of illumination. Further illumination causes deposition of a stable black film on the polar adsorbent. Mass spectrometry of the cold-trapped red intermediate shows clusters of peaks corresponding to the expected distribution of isotopomers of C(2)O(4)Br(4)(+), as well as of C(2)O(4)Br(3)(+). DFT computations indicate that the lowest-energy species with the formula C(2)O(4)Br(4) is trans-2,4-dibromo-2,4-dihypobromo-1,3-dioxetane. Formation of this molecule from (2CO(2) + 2Br(2)) would require a minimum of 3 visible photons, two of which would hypothetically be used in formation of as-yet undetected CO(2)Br(2) and the third, in a subsequent photodimerization. By elemental analysis, the final amorphous solid product contains a C/Br atomic ratio >12, suggesting that Br(2) is acting photocatalytically. Even with a poorly optimized optical system, the reaction rate has reached as high as 1.6 mg reduced C with 40 s of solar collection using a 30 cm diameter paraboloid reflector. This rate is consistent with the storage of approximately 1% of incident solar energy.

show abstract

“…Approximately, 0.5 Torr CO 2 was added to the reaction mixture to rapidly deactivate any photolytically generated spin-orbit excited bromine atoms. The rate coefficient for electronic-to-vibrational energy transfer from Br( 2 P 1/2 ) to CO 2 is known to be 1.5 × 10 −11 cm 3 molecule −1 s −1 [24]. This rapid thermalization of excited state bromine atoms avoided any problems associated with the difference in detection sensitivity and/or reactivity for the two atomic bromine electronic states.…”

Section: Experimental Techniquementioning

confidence: 97%

Kinetics of elementary steps in the reaction of atomic bromine with 2,3‐dimethyl‐2‐butene under atmospheric conditions

Laine

Sohn

Nicovich

et al. 2011

Int J of Chemical Kinetics

View full text Add to dashboard Cite

We have employed the laser flash photolysis-resonance fluorescence technique to investigate the gas-phase kinetics of elementary steps in the Br-initiated oxidation of 2,3-dimethyl-2-butene (TME) under atmospheric conditions. At T ≥ 274 K, measured rate coefficients are independent of pressure suggesting hydrogen abstraction as the dominant pathway. The following Arrhenius expression adequately describes all kinetic data at 274 K ≤ T ≤ 420 K: k 1a (T ) = (3.84 ± 0.84) × 10 −11 exp[(−169 ± 61)/T ] cm 3 molecule −1 s −1 (uncertainties are 2σ , precision only). At 203 K ≤ T ≤ 241 K, kinetic evidence for reversible addition, Br + TME ↔ Br−TME (k 1b , k −1b ), is observed. Analysis of the approach to equilibrium data allows evaluation of the rate coefficients k 1b and k −1b . At atmospheric pressure addition of Br to TME occurs at a near gas kinetic rate. Equilibrium constants are obtained from k 1b /k −1b . Combining the experimental results with electronic structure calculations allows third-law analyses of the equilibrium data. The following thermochemical parameters for the addition reaction (1b) at 0 and 298 K are obtained 14 LAINE ET AL.(standard state = 1 atm): r H 0 = −47.1 ± 3.0 kJ mol −1 , r H 298 = −47.3 ± 3.0 kJ mol −1 , and r S 298 = −101.5 ± 10.0 J mol −1 K −1 . Examination of the effect of added O 2 on Br atom kinetics under conditions where reversible adduct formation is observed allows determination of the rate coefficient for the Br-TME + O 2 reaction (k 2 ). At 223 K, we find that k 2 increases from 3.9 to 5.5 × 10 −12 cm 3 molecule −1 s −1 as pressure increases from 25 to 200 Torr. Our results suggest that under most atmospheric conditions the Br-TME reaction with O 2 occurs more rapidly than the Br-TME unimolecular decomposition. Hence, the fast addition reaction appears to control the rate of TME loss by reaction with Br in the atmosphere.

show abstract

Infrared molecular lasers pumped by electronic-vibrational energy transfer from Br(42P1/2): CO2, N2O, HCN, and C2H2

Cited by 72 publications

References 9 publications

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

Bromine-Sensitized Solar Photolysis of CO₂

Kinetics of elementary steps in the reaction of atomic bromine with 2,3‐dimethyl‐2‐butene under atmospheric conditions

Contact Info

Product

Resources

About

Infrared molecular lasers pumped by electronic-vibrational energy transfer from Br(42P1/2): CO2, N2O, HCN, and C2H2

Cited by 72 publications

References 9 publications

Temperature-Dependent Rate Coefficients for the Reactions of Br(2P3/2), Cl(2P3/2), and O(3PJ) with BrONO2

Temperature-Dependent Rate Coefficients for the Reactions of Br(2P3/2), Cl(2P3/2), and O(3PJ) with BrONO2

Bromine-Sensitized Solar Photolysis of CO2

Kinetics of elementary steps in the reaction of atomic bromine with 2,3‐dimethyl‐2‐butene under atmospheric conditions

Contact Info

Product

Resources

About

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

Temperature-Dependent Rate Coefficients for the Reactions of Br(²P_3/2), Cl(²P_3/2), and O(³P_J) with BrONO₂

Bromine-Sensitized Solar Photolysis of CO₂