Inversion Tunneling in Aniline from High Resolution Infrared Spectroscopy and an Adiabatic Reaction Path Hamiltonian Approach

Fehrensen, Benjamin; Luckhaus, David; Qüack, Martin

doi:10.1524/zpch.1999.209.part_1.001

Cited by 68 publications

(61 citation statements)

References 25 publications

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“…Recent experimental and theoretical studies show definitively that H 2 O 2 [17] [18] and aniline-NHD [19] with very low barriers for stereomutation, of ca. 5 kJ mol…”

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confidence: 99%

“…In this paper, we present our theoretical results for the mode-selective stereomutation tunneling in disulfane isotopomers. The calculations were performed employing the quasiadiabatic channel reaction-path Hamiltonian (RPH) approach [18] [19], which has been shown to reproduce well the experimentally observed pure torsional spectrum and mode-specific tunneling, as well as the few known isotope shifts for H 2 O 2 , a related molecule. The reaction path Hamiltonian used here is based on earlier work by Miller, Handy, and Adams [43], and further related to still earlier adiabatic channel model [44] [45] and transition-state-theory treatments [46].…”

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confidence: 99%

“…The reaction path Hamiltonian used here is based on earlier work by Miller, Handy, and Adams [43], and further related to still earlier adiabatic channel model [44] [45] and transition-state-theory treatments [46]. It has also been successfully applied to the inversion dynamics of aniline [19]. Moreover, it has been shown that our harmonic reaction-path Hamiltonian approach gives good agreement with the results of a new fully coupled six-dimensional adiabatic channel approach [18] [47].…”

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confidence: 99%

“…The torsional-tunneling dynamics were calculated with the quasiadiabatic channelreaction path Hamiltonian treatment described in detail in [18] [19]. In brief, it is a modified version of the RPH treatment introduced by Miller, Handy, and Adams [43].…”

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confidence: 99%

“…Avoided crossings of adiabatic channels are removed in the modified approach by a systematic deperturbation by means of 2 Â 2 diabatic rotations in normal coordinate space. For details, we refer to [18] [19]. The existing computer program package from [18] [19] was modified to allow for much higher numerical precision.…”

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confidence: 99%

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Mode Selective Stereomutation and Parity Violation in Disulfane Isotopomers H2S2, D2S2, T2S2

Gottselig

Luckhaus

Qüack

et al. 2001

HCA

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Dedicated to Edgar Heilbronner on the occasion of his 80th birthdayWe report quantitative calculations of stereomutation tunneling in the disulfane isotopomers H 2 S 2 , D 2 S 2 , and T 2 S 2 , which are chiral in their equilibrium geometry. The quasi-adiabatic channel, quasi-harmonic reaction path Hamiltonian approach used here treats stereomutation including all internal degrees of freedom. The torsional motion is handled as an anharmonic reaction coordinate in detail, whereas all the remaining degrees of freedom are taken into account approximately. We predict how stereomutation is catalyzed or inhibited by excitation of the various vibrational modes. The agreement of our theoretical results with spectroscopic data from the literature on H 2 S 2 and D 2 S 2 is excellent. We furthermore predict the influence of parity violation on stereomutation as characterized approximately by the ratio (DE pv /DE AE ) of the (local or vibrationally averaged) parity violating potential DE pv and the tunneling splittings DE AE in the symmetrical case. This ratio is exceedingly small for the reference molecules H 2 O 2 and D 2 O 2 , and still very small (2´10 À6 cm À1 ) for H 2 S 2 , which, thus, all exhibit essentially parity conservation in the dynamics. However, for D 2 S 2 it is ca. 0.002, and for T 2 S 2 it is ca. 1, which seems to be the first case where such intermediate mixing through parity violation is quantitatively predicted for spectroscopically accessible molecules. The consequences for the spectroscopic detection of molecular parity violation are discussed briefly also in relation to other molecules.

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“…Recent experimental and theoretical studies show definitively that H 2 O 2 [17] [18] and aniline-NHD [19] with very low barriers for stereomutation, of ca. 5 kJ mol…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Mode Selective Stereomutation and Parity Violation in Disulfane Isotopomers H2S2, D2S2, T2S2

Gottselig

Luckhaus

Qüack

et al. 2001

HCA

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Paritätsverletzung dominiert die Dynamik der Chiralität in Dischwefeldichlorid

et al. 2001

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Vor fast 75 Jahren führte Friedrich Hund den quantenmechanischen Tunneleffekt ein, [1] indem er den Ursprung molekularer Chiralität als De-facto-Symmetriebrechung [2] in Verbindung mit einer sehr kleinen Tunnelaufspaltung DE AE zwischen den Niveaus niedrigster Energie und delokalisierter Wellenfunktionen wohldefinierter Parität ( und À ) begründete. Nach Entdeckung der De-lege-Paritätsverletzung 1956 [3,4] erwarten wir heute eine kleine paritätsverletzende Energiedifferenz DE pv zwischen den beiden Enantiomeren eines chiralen Moleküls, die nach Berechnungen im Rahmen der elektroschwachen Quantenchemie, [5±7, 10] welche die paritätsverletzende Natur der schwachen Wechselwirkung berücksichtigt, für Moleküle aus leichteren Elementen etwa 10 À13AE3 J mol À1 beträgt. [5±12] Die Entdeckung, [6,7,10] dass jDE pv j um etwa eine Gröûenordnung gröûer ist als früher erwartet, hat der Suche nach molekularer Paritätsverletzung neuen Aufschwung verliehen. Unsere frühen Ergebnisse [6,7] wurden inzwischen durch weitere theoretische Berechnungen bestätigt. [10±12] Für typische, stabile chirale Moleküle mit einer hohen Barriere für die Umwandlung zwischen den Enantiomeren sollte jDE pv j in der Regel viel gröûer sein als die kleinen Tunnelaufspaltungen jDE AE j der niedrigsten Schwingungszustände. In diesem Fall haben die molekularen Eigenfunktionen wohldefinierte Händigkeit, und die molekulare Chiralität hat ihren Ursprung in einer De-lege-Symmetriebrechung. Obwohl diese bemerkenswerte Situation qualitativ vorhergesagt wird, [2,5] existiert bisher kein Fall, für den eine quantitative Rechnung gezeigt hätte, dass jDE pv j ) jDE AE j gilt und somit Chiralität durch De-lege-Paritätsverletzung dominiert wird. Hier berichten wir über das erste Beispiel dieser Art: Dischwefeldichlorid (ClSSCl, Abbildung 1).Dischwefeldichlorid hat eine C 2 -symmetrische Gleichgewichtsstruktur mit hohen Barrieren für die Umwandlung zwischen dem P-und dem M-Enantiomer (siehe Abbildung 2) und wurde schon früher sowohl experimentell als auch mit traditionellen (paritätserhaltenden) quantenchemischen Methoden im Zusammenhang mit anderen Verbindungen des Typs X 2 S 2 untersucht. [13±18] Unsere neuen Berechnungen der paritätsverletzenden Potentiale, der entsprechenden paritätsverletzenden Energiedifferenzen und der Torsionstunnelaufspaltung im Schwingungsgrundzustand ZUSCHRIFTEN

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