Mechanism of energy transfer in the triplet mercury photosensitization of paraffins

Gunning, H. E.; Campbell, J. M.; Saunhu, H. S.; Strausz, O. P.

doi:10.1021/ja00784a017

Cited by 18 publications

(4 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Excited states of Hg are known to be quenched by hydrocarbons via a hydrogen abstraction reaction to form the HgH species. 25 The secondary, steeper slope observed in Fig. 3 for the lake sediment samples, indicating a larger relative change in the b Tl values, would suggest an increased rate of formation of the Hg hydride species by comparison to the standards.…”

Section: Discussionmentioning

confidence: 83%

The effect of hydride formation on instrumental mass discrimination in MC-ICP-MS: a case study of mercury (Hg) and thallium (Tl) isotopes

Georg

Newman

2015

J. Anal. At. Spectrom.

View full text Add to dashboard Cite

Here we report evidence for enhanced hydride formation for Hg isotopes when using high sensitivity X skimmer cones and the Neptune MC-ICP-MS. The effect on the instrumental mass discrimination and the robustness of the Tl external mass-bias 20 correction was investigated. A series of experiments have been conducted to study the effect of variable Hg concentrations on the measured mass bias correction factor, ! Tl .The results of our experiments show a linear relation between the Hg concentration and the measured 205 Tl/ 203 Tl ratio of the internal standard. The resulting mass-bias correction factor ! Tl thus appears to be dependent on the analyte concentration, 25 questioning the applicability of Tl as an internal standard for high precision Hg isotope ratio measurements. These observations are consistent with the formation of Hg hydrides (HgH x where x = 1, 2). Numerical simulations show Hg hydride formation rates of 0.02 to 0.18% to be consistent with experimental observations, when using high-sensitivity X skimmer cones. Here we discuss the implications of Hg 30 hydride formation for Hg isotope ratio measurements and propose a set of precautionary steps that can help to identify and remediate analytical issues related to hydride formation. Whilst the effect of hydride formation on mass-dependent Hg isotope ratios can be controlled, mass independent Hg ratios are shown to be very sensitive to hydride formation. A comparison between different types of sediment 35 samples and standards also suggests a matrix dependency on hydride formation. We conclude that precise and accurate Hg isotope ratio determination using MC-ICP-MS is possible, however, probably not to low ppm-levels of precision.

show abstract

Section: Discussionmentioning

confidence: 83%

The effect of hydride formation on instrumental mass discrimination in MC-ICP-MS: a case study of mercury (Hg) and thallium (Tl) isotopes

Georg

Newman

2015

J. Anal. At. Spectrom.

View full text Add to dashboard Cite

show abstract

“…It is interesting that the anomalously high quenching cross sections for cyclopentane and cyclohexane were not treated in the earlier Hg^P^-RH theoretical papers. [2][3][4][5] In a classical study of Cd(3PJ-sensitized decomposition of c-C5H10,12 rough competitive quenching data indicates that the ratio of rates for CO and c-C5H10 quenching at 355 °C is ~8 ± 4. Assuming the quenching rate for CO is not very temperature dependent, the absolute quenching rate of CO at 280 °C7 can be used to calculate a quenching rate of Cd(3Pj) by c-C5H12 of ~(3 ± 1.5) X 109 M^1 s^1 at 355 °C.…”

Section: Discussionmentioning

confidence: 99%

Reaction of excited cadmium(3PJ) atoms with alkane hydrocarbons. Quenching cross sections and primary cadmium hydride yields

Breckenridge¹,

Renlund²

1979

J. Phys. Chem.

View full text Add to dashboard Cite

Publication costs assisted by the Petroleum Research Fund Absolute cross sections for the quenching of Cd(3P,/) by several alkane hydrocarbons have been determined using the resonance-radiation flash photolysis technique. Yields of CdH from the alkanes as compared to the CdH yield in the reaction of Cd(3PJ with H2 were also determined. The Cd(3P.y) quenching cross sections for the normal alkanes are four orders of magnitude smaller than the cross section for quenching by H2) even though CdH formation is exothermic for the alkanes and only thermoneutral for H2. The CdH yields from Cd(3Pj) quenching for propane and isobutane are equal within experimental error to the CdH yield for H2, and it is suggested that this yield is probably unity. In marked contrast to the quenching of the valence isoelectronic species Hg(3P0) and Hg(3Pi) by the alkanes, there is virtually no dependence of the Cd(3Pj) quenching rate on C-H bond strength, and none of the theories advanced to explain the Hg(3Pj) interaction with C-H bonds can account for the Cd(3Py) results. A mechanism is tentatively suggested in which a loose complex is formed between Cd(3Pj) and alkane molecules, followed by a low-probability potential surface crossing which has little dependence on C-H bond strength, or at least can occur with primary C-H bonds. It is also suggested that differences between Cd(3Pj) and Hg(3Py) quenching by the alkanes can be understood if the mechanistic pathways which account for the Hg(3Pj) results are merely energetically inaccessible to the lower-energy Cd(3Pj) state at moderate temperatures.

show abstract

“…Theoretical work has progressed slowly, primarily because of the difficulty in calculation of pertinent potential energy surfaces. A summary of early work is presented by Mitchell and Zemansky.10 A discussion of theoretical efforts concerning Hg(3Pi) quenching is included in a recent review on electronic energy transfer by Cundall.41 The recent paper by Gunning,et al,38 includes a review of work on the mechanism of quenching by the alkanes. The authors hope that the results of this study will contribute to further elucidation of these interactions.…”

Section: Discussionmentioning

confidence: 99%

Absolute quenching cross sections of Hg(3P1) with various molecules

Michael¹,

Suess²

1974

J. Phys. Chem.

View full text Add to dashboard Cite

Publication costs assisted by the U. S. Atomic Energy CommissionThe absolute quenching cross sections for Hg(3P1) with a number of quenching gases have been obtained in a steady-state photolytic experiment. The intensity of 2537-8, emission has been followed as a function of absorbed intensity, and also pressure of the quenching gas. Low Hg concentrations are maintained in order to avoid the complication of radiation imprisonment. Quenching rate constants are determined from modified Stern-Volmer plots. The results are compared to cross sections from Zemansky type experiments on a relative basis and in several cases to the absolute results of Yarwood, Strausz, and Gunning who applied Holstein theory to Zemansky type experimental results. Comparison is also made to other low opacity studies and, where possible, to the relative cross sections determined from chemical methods. Generally, good agreement is obtained. NO provides the only gross disagreement in these comparisons of the nine molecules studied. IntroductionThe quenching of the 3P1 state of mercury by a foreign gas represents probably the most extensively investigated and most useful primary photochemical system. The fundamental photophysical processes in this system are indicated in the following mechanism

show abstract

Mechanism of energy transfer in the triplet mercury photosensitization of paraffins

Cited by 18 publications

References 5 publications

The effect of hydride formation on instrumental mass discrimination in MC-ICP-MS: a case study of mercury (Hg) and thallium (Tl) isotopes

The effect of hydride formation on instrumental mass discrimination in MC-ICP-MS: a case study of mercury (Hg) and thallium (Tl) isotopes

Reaction of excited cadmium(3PJ) atoms with alkane hydrocarbons. Quenching cross sections and primary cadmium hydride yields

Absolute quenching cross sections of Hg(3P1) with various molecules

Contact Info

Product

Resources

About