CARS investigations of quenching and photochemical reactions in the Na+H2 collision system

Pichler, Goran; Motzkus, Marcus; Cunha, Silvio Luiz Souza; Kompa, K. L.; Correia, Ricardo Rego Bordalo; Hering, P.

doi:10.1007/bf02455368

Cited by 21 publications

(8 citation statements)

References 9 publications

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“…We have chosen the electronic quenching process of Na ( 3p 2 P) by H 2 in order to demonstrate the multiple spawning method for polyatomic molecules. This is one of the most well-studied electronic quenching processes ,− and is important as a paradigm for electronic quenching. There is a conical intersection connecting the ground and first excited electronic states, corresponding to Na( 3p 2 P) + H 2 and Na( 3s 2 S) + H 2 .…”

Section: Electronic Quenching In Na* + H2mentioning

confidence: 99%

Molecular Collision Dynamics on Several Electronic States

1997

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A time-dependent quantum mechanical method for propagating the wave function on several electronic states is discussed for the polyatomic case and illustrated by the quenching collision of a Na (3p 2P) atom by H2. The specification of method is governed by the need to have a clear physical interpretation of the results, by the recognition that the motion on a given electronic state can often (but not always) be well approximated by classical mechanics, and by the need for a computational procedure that is simple enough to handle polyatomic systems. These desiderata are realized by the spawning technique which is discussed in detail. One more feature of the method is that it allows for a smooth interface with the methodologies of quantum chemistry so that the electronic structure problem can be solved simultaneously with the time propagation of the nuclear dynamics. The method is derived from a variational principle and so can yield quantum mechanically numerically converged results. The parameters that govern the numerical accuracy of the method are explicitly discussed with special reference to their physical significance. The quenching of a Na (3p 2P) atom by H2 due to a conical intersection of two potential energy surfaces is used as a computational example since it illustrates many of the features of the method. This collision is found to be sticky and exhibits many sequential nonadiabatic couplings, each of which is localized in time, where the quenching probability per traversal of the conical intersection region is small. However, the accumulated transfer of population to the ground state can be significant since the duration of the overall transfer is spread over many vibrational periods of H2.

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Section: Electronic Quenching In Na* + H2mentioning

confidence: 99%

Molecular Collision Dynamics on Several Electronic States

1997

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“…Further control experiments could entail manipulation of the rovibrational population distribution of the H 2 molecule after the collision, which could be detected by ns CARS [156,159,180], or opening the NaH formation channel. It should be noted that this (reactive) channel has already been observed in the above experiments ("laser snow") [181,182,192,193]. The door to control experiments on the NaH 2 exciplex, as already described theoretically, is very nearly open.…”

Section: Discussionmentioning

confidence: 95%

Evolutionary algorithms and their application to optimal control studies

et al. 2001

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“…The details of the heat-pipe oven with the sodium vaporÈhydrogen gas Ðlling have been described in ref. 7. The present experiment was performed at a lower temperature of 520 K measured with a thermocouple within the heat-pipe oven.…”

Section: Methodsmentioning

confidence: 99%

“…7,8 In this work, we were interested in the NaH decay behavior on a time-scale much longer than the initial formation period and the longest vibrational relaxation time (ca. 150 ns at 100 hPa pressure).…”

Section: Introductionmentioning

confidence: 99%

Determination of the reaction dynamics of sodium hydride in a hydrogen atmosphere with degenerate four-wave mixing

Lehr

Motzkus

Pichler

et al. 1998

J. Raman Spectrosc.

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Degenerate four-wave mixing was successfully applied to the determination of the reactive and di †usive loss mechanisms of photochemically produced sodium hydride in and atmospheres and in a Na + H 2 Na + H 2 + Ar supplement argon Ðlling. Sodium hydride is formed on the microsecond time-scale in a quenching-reaction sequence after the 3s-3p excitation of sodium in the excitation volume. The concentration of NaH decreases with time depending on the bu †er gas pressure. For small pressures (AE20 hPa) di †usion out of the detection volume is the predominant process. The binary di †usion constant of sodium hydride in hydrogen was determined to be 0.66 » 0.07 cm2 s-1 at 1013 hPa and 273 K. Moreover, experimental data show an additional reactive loss mechanism present at high gas pressures. A second-order reaction with a thermal rate constant of k 2 = 3.8 Â 10-7 cm-3 s-1 (r = 5.6 Â 10-12 cm2) at 520 K was observed. The thermal rate constant is independent of the hydrogen partial pressure, indicating that the reaction is most probable. The activation energy of NaH + NaH Ç Na 2 + H 2 the reaction was estimated to be of the order of 0.9 eV.

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CARS investigations of quenching and photochemical reactions in the Na+H2 collision system

Cited by 21 publications

References 9 publications

Molecular Collision Dynamics on Several Electronic States

Molecular Collision Dynamics on Several Electronic States

Evolutionary algorithms and their application to optimal control studies

Determination of the reaction dynamics of sodium hydride in a hydrogen atmosphere with degenerate four-wave mixing

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