The Rotational Spectrum of the Fluorobenzene-Argon Van der Waals Complex

Stahl, Wolfgang; Grabow, Jens-Uwe

doi:10.1515/zna-1992-0508

Cited by 43 publications

(28 citation statements)

References 9 publications

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“…This is the approach taken by Stahl and Grabow in their study of S 0 FB-Ar. 7 In that case the FB geometry determined by Doraiswamy and Sharma 32 was used as the basis for determining the FB-Ar geometry. Unfortunately, in the case of S 1 FB the experimental geometry is unknown so, instead, we use the result of ab initio calculations to determine the complex geometry using this approach.…”

Section: A Fb-ar S 1 Rotational Constants and Geometrymentioning

confidence: 99%

“…For each electronic state the calculations provide a number of predictions, including the van der Waals vibrational states in the lower region of the vibrational manifold, the molecular geometry and the binding energy. Currently, experimental data are available concerning the S 0 and S 1 binding energies, 5,6 the S 0 rotational constants, 7,8 and hence S 0 geometry, and a number of the S 1 van der Waals vibrational levels. 5,6,[9][10][11] However, the S 1 rotational constants, and hence the S 1 geometry for the complex, have yet to be satisfactorily determined 4 and, with the exception of the two bend fundamentals, 12 the S 0 van der Waals vibrational level structure remains unobserved.…”

Section: Introductionmentioning

confidence: 99%

“…The ground state geometry of the complex has been inferred from the known FB geometry and the FB-Ar rotational constants determined using microwave studies. 7,8 Two structures satisfy the rotational constants. These differ in the direction of displacement of the Ar atom from the FB centre of mass (CoM), with Ar being either towards the C-F bond or towards the centre of the ring.…”

Section: Introductionmentioning

confidence: 99%

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Two-dimensional laser induced fluorescence spectroscopy of van der Waals complexes: Fluorobenzene-Arn (n = 1,2)

Gascooke

Alexander

Lawrance

2012

The Journal of Chemical Physics

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The technique of two-dimensional laser induced fluorescence (2D-LIF) spectroscopy has been used to observe the van der Waals complexes fluorobenzene-Ar and fluorobenzene-Ar2 in the region of their S1-S0 electronic origins. The 2D-LIF spectral images reveal a number of features assigned to the van der Waals vibrations in S0 and S1. An advantage of 2D-LIF spectroscopy is that the LIF spectrum associated with a particular species may be extracted from an image. This is illustrated for fluorobenzene-Ar. The S1 van der Waals modes observed in this spectrum are consistent with previous observations using mass resolved resonance enhanced multiphoton ionisation techniques. For S0, the two bending modes previously observed using a Raman technique were observed along with three new levels. These agree exceptionally well with ab initio calculations. The Fermi resonance between the stretch and bend overtone has been analysed in both the S0 and S1 states, revealing that the coupling is stronger in S0 than in S1. For fluorobenzene-Ar2 the 2D-LIF spectral image reveals the S0 symmetric stretch van der Waals vibration to be 35.0 cm−1, closely matching the value predicted based on the fluorobenzene-Ar van der Waals stretch frequency. Rotational band contour analysis has been performed on the fluorobenzene-Ar $\overline {0_0^0 }$000¯ transition to yield a set of S1 rotational constants A′ = 0.05871 ± 0.00014 cm−1, B′ = 0.03803 ± 0.00010 cm−1, and C′ = 0.03103 ± 0.00003 cm−1. The rotational constants imply that in the S1 00 level the Ar is on average 3.488 Å from the fluorobenzene centre of mass and displaced from it towards the centre of the ring at an angle of ∼6° to the normal. The rotational contour for fluorobenzene-Ar2 was predicted using rotational constants calculated on the basis of the fluorobenzene-Ar geometry and compared with the experimental contour. The comparison is poor which, while due in part to expected saturation effects, suggests the presence of another band lying beneath the contour.

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Section: A Fb-ar S 1 Rotational Constants and Geometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Two-dimensional laser induced fluorescence spectroscopy of van der Waals complexes: Fluorobenzene-Arn (n = 1,2)

Gascooke

Alexander

Lawrance

2012

The Journal of Chemical Physics

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“…The value for the van der Waals bond length, R 0 , is that determined from the FB-Ar rotational constants extracted from the microwave spectrum. 25 With these values and the FB and Ar masses, we have determined a set of FB-Ar 2 (1|1) vibrational frequencies based on FB-Ar values of 22.3, 33.7, and 41.8 cm −1 for the long axis bend, short axis bend and stretch, respectively. The bend values are those observed, while the stretch value is that obtained by de-perturbing the Fermi resonance.…”

Section: B the Fb-ar 2 (1|1) Van Der Waals Vibrationsmentioning

confidence: 99%

Intermolecular vibrations of fluorobenzene-Ar up to 130 cm−1 in the ground electronic state

Gascooke¹,

Alexander²,

Lawrance³

2012

The Journal of Chemical Physics

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Sixteen intermolecular vibrational levels of the S 0 state of the fluorobenzene-Ar van der Waals complex have been observed using dispersed fluorescence. The levels range up to ∼130 cm −1 in vibrational energy. The vibrational energies have been modelled using a complete set of harmonic and quartic anharmonic constants and a cubic anharmonic coupling between the stretch and long axis bend overtone that becomes near ubiquitous at higher energies. The constants predict the observed band positions with a root mean square deviation of 0.04 cm −1 . The set of vibrational levels predicted by the constants, which includes unobserved bands, has been compared with the predictions of ab initio calculations, which include all vibrational levels up to 70-75 cm −1 . There are small differences in energy, particularly above 60 cm −1 , however, the main differences are in the assignments and are largely due to the limitations of assigning the ab initio wavefunctions to a simple stretch, bend, or combination when the states are mixed by the cubic anharmonic coupling. The availability of these experimental data presents an opportunity to extend ab initio calculations to higher vibrational energies to provide an assessment of the accuracy of the calculated potential surface away from the minimum. The intermolecular modes of the fluorobenzene-Ar 2 trimer complex have also been investigated by dispersed fluorescence. The dominant structure is a pair of bands with a ∼35 cm −1 displacement from the origin band. Based on the set of vibrational modes calculated from the fluorobenzene-Ar frequencies, they are assigned to a Fermi resonance between the symmetric stretch and symmetric short axis bend overtone. The analysis of this resonance provides a measurement of the coupling strength between the stretch and short axis bend overtone in the dimer, an interaction that is not directly observed. The coupling matrix elements determined for the fluorobenzeneAr stretch-long axis bend overtone and stretch-short axis bend overtone couplings are remarkably similar (3.8 cm −1 cf. 3.2 cm −1 ). Several weak features seen in the fluorobenzene-Ar 2 spectrum have also been assigned.

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“…where g is the direction cosine between internal and principal inertia axis g ϭ a, b, c ( z, x, y in I r ), P g is the component of total angular momentum operator, p is the total angular momentum operator of the internal rotor, I g is the moment of inertia derived from the structure of the complex, I ␣ is the moment of inertia of the internal rotor about its internal rotation and C 3 symmetry axis, and V(␣) is the potential function in equation [1] of internal rotation.…”

Section: Theorymentioning

confidence: 99%