Vibrational predissociation in <i>S</i>1 1-methylindole van der Waals clusters

Outhouse, E. Allison; Demmer, David; Leach, Gary W.; Wallace, Stephen C.

doi:10.1063/1.465707

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…The properties of the β′-relaxation in 1MID uncovered by application of pressure, together with the absence of intramolecular transition, tautomers and conformers demonstrated before by experiments, , leave the in-plane rotation in this planar molecule of rather large size (see the inset of Figure b) as its only possible origin . The possibly large angular displacements of the in-plane rotation gives rise to the more intense β′-relaxation to eclipse the JG β-relaxation nearby, which involves out-of-plane rotation of 1MID.…”

mentioning

confidence: 69%

“…The dynamic and thermodynamic properties of 1MID at ambient pressure have been reported in refs 29 and 33 showing β KWW = 0.53 near the glass transition temperature T g = 181 K. Its chemical structure (Figure 1b) shows that it is a rigid and planar molecule, and the absence of intramolecular transition, tautomers, and conformers was demonstrated. 34,35 We performed isothermal dielectric relaxation measurements at elevated pressures P. Representative loss spectra, ε″(f), at 215 K are presented as an example in Figure 1. At lower pressures of up to 300 MPa where 1MID remains in the liquid state, a single secondary loss peak is present together with the α-loss peak in Figure 1a.…”

mentioning

confidence: 99%

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Direct Evidence of Relaxation Anisotropy Resolved by High Pressure in a Rigid and Planar Glass Former

Valenti

Ngai

et al. 2017

J. Phys. Chem. Lett.

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Rigid molecular glass-formers with no internal degrees of freedom nonetheless have a single secondary β-relaxation. For a rigid and planar molecule, 1-methylindole (1MID), although a secondary relaxation is resolved at ambient pressure, its properties do not conform to the rules established for rigid molecules reported in early studies. By applying pressure to the dielectric spectra of 1MID, we find the single secondary relaxation splits into two. The slower one is pressure sensitive showing connections to the α-relaxation as observed in other rigid molecules, while the faster one is almost pressure insensitive and dominate the loss at ambient pressure. The two secondary relaxations, identified to associate with the out-of-plane and in-plane rotations of the rigid and planar 1MID, are resolved and observed for the first time by increasing density via elevating pressure.

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confidence: 69%

mentioning

confidence: 99%

Direct Evidence of Relaxation Anisotropy Resolved by High Pressure in a Rigid and Planar Glass Former

Valenti

Ngai

et al. 2017

J. Phys. Chem. Lett.

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“…In particular, for 1MID, the absence of intramolecular transitions and different tautomers or conformers has been demonstrated. [60][61][62] The same applies to both FIG. 5.…”

Section: Methodsmentioning

confidence: 99%

Secondary relaxation dynamics in rigid glass-forming molecular liquids with related structures

Wang

Liu

et al. 2015

The Journal of Chemical Physics

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The dielectric relaxation in three glass-forming molecular liquids, 1-methylindole (1MID), 5H-5-Methyl-6,7-dihydrocyclopentapyrazine (MDCP), and Quinaldine (QN) is studied focusing on the secondary relaxation and its relation to the structural α-relaxation. All three glass-formers are rigid and more or less planar molecules with related chemical structures but have dipoles of different strengths at different locations. A strong and fast secondary relaxation is detected in the dielectric spectra of 1MID, while no resolved β-relaxation is observed in MDCP and QN. If the observed secondary relaxation in 1MID is identified with the Johari-Goldstein (JG) β-relaxation, then apparently the relation between the α- and β-relaxation frequencies of 1MID is not in accord with the Coupling Model (CM). The possibility of the violation of the prediction in 1MID as due to either the formation of hydrogen-bond induced clusters or the involvement of intramolecular degree of freedom is ruled out. The violation is explained by the secondary relaxation originating from the in-plane rotation of the dipole located on the plane of the rigid molecule, contributing to dielectric loss at higher frequencies and more intense than the JG β-relaxation generated by the out-of-plane rotation. MDCP has smaller dipole moment located in the plane of the molecule; however, presence of the change of curvature of dielectric loss, ε″(f), at some frequency on the high-frequency flank of the α-relaxation reveals the JG β-relaxation in MDCP and which is in accord with the CM prediction. QN has as large an in-plane dipole moment as 1MID, and the absence of the resolved secondary relaxation is explained by the smaller coupling parameter than the latter in the framework of the CM.

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“…[43][44][45][46][47][48] In the modeling for pDFB-Ar and pDFB-N 2 , the relaxation dynamics from the initially pumped S 1 complex level always begins with IVR to isoenergetic levels comprised of a lower S 1 ring level in combination with an excited set of van der Waals modes. A number of applications of this model give evidence of its basic integrity.…”

Section: Modeling Of Dissociation In Pdfb Van Der Waals Complexesmentioning

confidence: 99%

Characteristics and relaxation dynamics of van der Waals complexes between p-difluorobenzene and Ne

Jayasekharan

Parmenter²

2004

The Journal of Chemical Physics

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Characteristics of the single and double Ne van der Waals complexes of p-difluorobenzene (pDFB) have been explored with ultraviolet fluorescence excitation and dispersed fluorescence spectroscopy. Eight S(1)-S(0) fluorescence excitation bands involving six ring modes of pDFB-Ne and two bands of pDFB-Ne(2) have been identified. Band assignments are confirmed by dispersed fluorescence from the pumped band. Shifts of the complex bands from the analogous monomer bands are generally 4 cm(-1) to the red for pDFB-Ne and 8 cm(-1) for pDFB-Ne(2). None of the observed ring modes is significantly perturbed by complexation in either the S(1) or S(0) states. The pDFB-Ne S(1) van der Waals binding energy D(0')

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Vibrational predissociation in S1 1-methylindole van der Waals clusters

Cited by 12 publications

References 15 publications

Direct Evidence of Relaxation Anisotropy Resolved by High Pressure in a Rigid and Planar Glass Former

Direct Evidence of Relaxation Anisotropy Resolved by High Pressure in a Rigid and Planar Glass Former

Secondary relaxation dynamics in rigid glass-forming molecular liquids with related structures

Characteristics and relaxation dynamics of van der Waals complexes between p-difluorobenzene and Ne

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