Electronic Spectroscopy of Toluene in Helium Nanodroplets: Evidence for a Long-Lived Excited State

Shepperson, Benjamin; Tandy, J. D.; Boatwright, Adrian; Cheng, Feng; Spence, D.; Shirley, Andrew; Yang, Shengfu; Ellis, Andrew M.

doi:10.1021/jp407577m

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Full details of the apparatus and techniques employed here can be found in previous publications. , In brief, helium nanodroplets with a mean size close to 5000 helium atoms were formed by expanding precooled gaseous helium into a vacuum through a 5 μm pinhole. The droplets then passed through two consecutive pick-up cells, the first containing NaCl vapor and the second methanol vapor.…”

Section: Methodsmentioning

confidence: 99%

Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets

et al. 2016

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Infrared (IR) spectra of complexes between NaCl and methanol have been recorded for the first time. These complexes were formed in liquid helium nanodroplets by consecutive pick-up of NaCl and CH 3 OH molecules. For the smallest NaCl(CH 3 OH) n , complexes where n = 1−3, the IR data suggest that the lowest-energy isomer is the primary product in each case. The predominant contribution to the binding comes from ionic hydrogen bonds between the OH in each methanol molecule and the chloride ion in the NaCl, as established by the large red shift of the OH stretching bands compared with the isolated CH 3 OH molecule. For n ≥ 4, there is a dramatic shift from discrete vibrational bands to very broad absorption envelopes, suggesting a profound change in the structural landscape and, in particular, access to multiple low-energy isomers. ■ INTRODUCTIONAlkali halides (MX) are archetypal univalent salts. The crystalline structure of the solid is disrupted by water, and these salts readily dissolve to form separated ions in dilute aqueous solutions. If the solid represents one extreme, then the counterpart is an isolated MX molecule. How might this smallest entity of salt, a single MX molecule, behave in the presence of a small water cluster, (H 2 O) n ? This problem can be addressed in experiments by forming isolated MX(H 2 O) n complexes and then using techniques, such as spectroscopy, to determine their properties. Such studies offer insight into the interaction between the constituent ionic particles and the solvent and can be reinforced through quantum chemical calculations. Understanding these interactions and the balance between them is critical in being able to carry out accurate simulations of bulk solutions. An early infrared (IR) spectroscopic study of a NaCl/H 2 O mixture in an argon matrix provided a tentative assignment of vibrational bands of the NaCl(H 2 O) complex.2 The first detailed spectroscopic study of several different NaCl(H 2 O) n complexes (n = 1−3) was obtained by microwave spectroscopy, and this revealed important structural information. 3,4 We have recently shown that complexes between NaCl and water molecules can be formed inside liquid helium nanodroplets, and this made it possible to record the first IR spectra of several small NaCl(H 2 O) n complexes. 5 The spectra for n = 1−3 are consistent with structures in which an ionic hydrogen bond (IHB) is formed between a single OH group in each water molecule and the Cl − in the salt. Evidence for interwater hydrogen bonding only begins to appear for n ≥ 4.An alternative solvent to water is methanol. Most solid alkali halides will dissolve in methanol, but their solubility is far lower than that in water. 6,7 The reduced solubility of salts in methanol when compared with that in water is a consequence of the hydrophobic (CH 3 ) group in the former. It would therefore be interesting to investigate how this amphiphilic character affects the interactions between a single salt molecule and one or more methanol molecules. It is well-known that...

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Section: Methodsmentioning

confidence: 99%

Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets

et al. 2016

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“…Full details of the apparatus can be found in previous publications. , In brief, helium nanodroplets with a mean size close to 5000 helium atoms were formed by expanding precooled gaseous helium into a vacuum through a 5 μm pinhole. The droplets then passed through a pick-up cell, where dopants were added.…”

Section: Experimental Sectionmentioning

confidence: 99%

Infrared Spectroscopy of Methanol and Methanol/Water Clusters in Helium Nanodroplets: The OH Stretching Region

2017

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Infrared (IR) spectra of methanol clusters in helium nanodroplets are reported in the OH stretching region for the first time. A simple series of intense bands are seen which almost perfectly match previous gas phase studies of these clusters and which are consistent with cyclic structures for the trimer and larger clusters. This finding differs from an earlier report of (CHOH) clusters in helium nanodroplets, which focused on the CO stretching region and concluded that while the trimer was cyclic, the tetramer and pentamer adopted branched structures based on a cyclic trimer core. We also present preliminary data for small (CHOH)(HO) clusters, and in particular, we report the first IR spectra for (CHOH)(HO) and (CHOH)(HO). Supporting ab initio calculations suggest that, like the pure methanol clusters, cyclic structures are adopted by these mixed solvent clusters in helium droplets.

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“…So, helium-droplet media combine the benefits of both the gas phase and the classical matrix-isolation techniques. As a result, this media is used as a powerful tool for spectroscopic studies, ranging from microwave and infrared spectroscopy of small molecules to electronic spectroscopy of molecular complexes at very low temperatures. ,,− …”

Section: Introductionmentioning

confidence: 99%

Structures and Photoelectron Spectra of Helium Nano Clusters

Dehdashti-Jahromi

Farrokhpour

2015

J. Phys. Chem. C

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The ionization energies and photoelectron spectra of van der Waals (vdW) Helium nano clusters (Hen) were studied in this work. The clusters with different number of helium atoms, in the range from n=2 to n=100, and belong to different symmetry point groups were selected.Density functional theory (DFT) employing CAM-B3LYP functional and 6-31+G(d) basis set were used for optimizing the structures. Symmetry adapted cluster-configuration interaction (SAC-CI) methodology and 6-31+G(3df) basis set were also used to calculate the ionization energies and their intensities. The calculated ionization energies and their intensities were used to simulate the photoelectron spectrum of each structure. It was found that the clustering of He atoms decreases the first ionization energy of the cluster compared to the isolated helium atom in the gas phase. The variation of the first ionization energies of the nanostructures were plotted versus their sizes and fitted into a mathematical equation. The simulated photoelectron spectra of the nano clusters were compared with each other comprehensively to investigate the change in the shape of spectrum with the size of cluster. The calculated ionization bands of each cluster were assigned using natural bonding orbital (NBO) analysis and their changes with the size were studied. Also, it was studied that how much the ionization processes is governed by the electron correlation and effect of the size on the electron correlation was examined.

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Electronic Spectroscopy of Toluene in Helium Nanodroplets: Evidence for a Long-Lived Excited State

Cited by 3 publications

References 22 publications

Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets

Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets

Infrared Spectroscopy of Methanol and Methanol/Water Clusters in Helium Nanodroplets: The OH Stretching Region

Structures and Photoelectron Spectra of Helium Nano Clusters

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Electronic Spectroscopy of Toluene in Helium Nanodroplets: Evidence for a Long-Lived Excited State

Cited by 3 publications

References 22 publications

Infrared Spectroscopy of NaCl(CH3OH)n Complexes in Helium Nanodroplets

Infrared Spectroscopy of NaCl(CH3OH)n Complexes in Helium Nanodroplets

Infrared Spectroscopy of Methanol and Methanol/Water Clusters in Helium Nanodroplets: The OH Stretching Region

Structures and Photoelectron Spectra of Helium Nano Clusters

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Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets

Infrared Spectroscopy of NaCl(CH₃OH)_n Complexes in Helium Nanodroplets