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Infrared spectroscopic studies of weakly bound clusters isolated in solid parahydrogen (pH2) that exhibit large-amplitude tunneling motions are needed to probe how quantum solvation perturbs these types of coherent dynamics. We report high resolution Fourier transform infrared absorption spectra of (HCl)2, HCl–DCl, and (DCl)2 isolated in solid pH2 in the 2.4–4.8 K temperature range. The (HCl)2 spectra show a remarkable amount of fine structures that can be rigorously assigned to vibration–rotation–tunneling transitions of (HCl)2 trapped in double substitution sites in the pH2 matrix where end-over-end rotation of the cluster is quenched. The spectra are assigned using a combination of isotopically (H/D and 35Cl/37Cl) enriched samples, polarized IR absorption measurements, and four-line combination differences. The interchange-tunneling (IT) splitting in the ground vibrational state for in-plane and out-of-plane H35Cl–H37Cl dimers is 6.026(1) and 6.950(1) cm−1, respectively, which are factors of 2.565 and 2.224 smaller than in the gas phase dimer. In contrast, the (DCl)2 results show larger perturbations where the ground vibrational state IT splitting in D35Cl–D37Cl is 1.141(1) cm−1, which is a factor of 5.223 smaller than in the gas phase, and the tunneling motion is quenched in excited intramolecular vibrational states. The results are compared to similar measurements on (HCl)2 made in liquid helium nanodroplets to illustrate the similarities and differences in how both these quantum solvents interact with large amplitude tunneling motions of an embedded chromophore. [ABSTRACT FROM AUTHOR]

Atomic and molecular clusters are a unique class of substances with properties that differ greatly from those of the bulk or single atoms due to changes in surface to volume ratio and finite size effects. Here, we demonstrate the ability to create cluster matter films using helium droplet mediated cluster assembly and deposition, a recently developed methodology that condenses atoms or molecules within liquid helium droplets and then gently deposits them onto a surface. In this work, we examine magnesium nanocluster films, which exhibit growth behavior comparable to low-energy cluster beam methods, and demonstrate physical properties and morphology dependent on helium droplet size. [ABSTRACT FROM AUTHOR]

We report the first rotationally resolved and completely assigned rovibrational spectrum for a nonhydride molecule rotating in the solid phase: carbon monoxide (CO) monomers isolated in cryogenic solid parahydrogen (p-H2). We employ a modified crystal field theory model, in which the CO molecular spectroscopic constants are taken as adjustable parameters, to make good spectroscopic assignments for all the observed features. We discuss the limitations of this approach and highlight the need for improved theoretical models of molecular rotation dynamics in quantum solids. [ABSTRACT FROM AUTHOR]

The ionization and charge transfer processes, which occur when a doped helium droplet undergoes electron impact, are studied for droplets doped with van der Waals complexes with various structures and electrostatic moments. The mass spectra of the two isomers of hydrogen cyanide complexed with either cyanoacetylene or acetylene in helium droplets were obtained using optically selected mass spectrometry, and show that the structure of the complex has a large effect on the fragmentation pattern. The resulting fragmentation pattern is consistent with an ionization process in which charge steering strongly influences the site of initial ionization. The observed dissociation products may also be subject to caging by the helium matrix. [ABSTRACT FROM AUTHOR]

We report polarized infrared absorption spectra of water isotopologues isolated in solid parahydrogen (pH2) which reveal the crystal field induced splittings of the 101←000 R(0) lines in the ν1 HDO, ν3 D2O, ν3 HDO, and ν3 H2O fundamental bands. For annealed pH2 solids, these spectra also reveal a strong alignment of the hexagonal-close-packed crystallites’ c axes with the deposition substrate surface normal. This alignment effect explains our failure to detect the parallel-polarized components of these R(0) lines in spectra of pH2 solids produced on a transparent deposition substrate [M. E. Fajardo et al., J. Mol. Struct. 695, 111 (2004)]. This lesson applies more generally to comparison of solid pH2 spectra obtained in different laboratories. The spectra are consistent with water monomers existing in solid pH2 as very slightly hindered rotors. The individual components of the R(0) absorption lines show a Lorentzian lineshape, with vibrational depopulation the most important source of line broadening. [ABSTRACT FROM AUTHOR]

Infrared spectroscopic studies of weakly bound clusters isolated in solid parahydrogen (pH 2 ) that exhibit large-amplitude tunneling motions are needed to probe how quantum solvation perturbs these types of coherent dynamics. We report high resolution Fourier transform infrared absorption spectra of (HCl) 2 , HCl-DCl, and (DCl) 2 isolated in solid pH 2 in the 2.4-4.8 K temperature range. The (HCl) 2 spectra show a remarkable amount of fine structures that can be rigorously assigned to vibration-rotation-tunneling transitions of (HCl) 2 trapped in double substitution sites in the pH 2 matrix where end-over-end rotation of the cluster is quenched. The spectra are assigned using a combination of isotopically (H/D and 35 Cl/ 37 Cl) enriched samples, polarized IR absorption measurements, and four-line combination differences. The interchange-tunneling (IT) splitting in the ground vibrational state for in-plane and out-of-plane H 35 Cl-H 37 Cl dimers is 6.026(1) and 6.950(1) cm -1 , respectively, which are factors of 2.565 and 2.224 smaller than in the gas phase dimer. In contrast, the (DCl) 2 results show larger perturbations where the ground vibrational state IT splitting in D 35 Cl-D 37 Cl is 1.141(1) cm -1 , which is a factor of 5.223 smaller than in the gas phase, and the tunneling motion is quenched in excited intramolecular vibrational states. The results are compared to similar measurements on (HCl) 2 made in liquid helium nanodroplets to illustrate the similarities and differences in how both these quantum solvents interact with large amplitude tunneling motions of an embedded chromophore.