Matrix isolation studies of CO2 clusters emerging from adiabatic expansion

Knoezinger, Erich; Beichert, P.

doi:10.1021/j100014a006

Cited by 27 publications

(24 citation statements)

References 4 publications

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“…The envelope for n > 2 shows two maxima, one around 4 to 5, the other around 11 to 12 HCN units. Previous studies on CH 3CN (dipole-dipole interactions [15]) and CO 2 (quadrupole-quadrupole interactions [16]) clearly exhibit a monotonous decrease of intensity with increasing cluster size. The peaks for n = 1 (not shown in Fig.…”

Section: Introductionmentioning

confidence: 78%

“…The clusters are subsequently isolated in a rare gas matrix and monitored by FTIR spectroscopy via the CH stretching vibration as effective probe. The combination of molecular beam and matrix isolation technique had previously been applied to CH 3CN [15] and CO 2 [16] in order to study the transition from the isolated molecule to the extended condensed phase. analysis of the harmonic vibrational frequencies is carried out by computing the second derivatives of the energy.…”

Section: Introductionmentioning

confidence: 99%

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HCN Clusters in Molecular Beams and Cryogenic Matrices

Beichert

Pfeiler

Knözinger

1995

Ber Bunsenges Phys Chem

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Cluster formation of hydrogen cyanide (HCN) was traced by mass spectroscopy in molecular beams and by FTIR spectroscopy in cryogenic matrices in which the clusters were embedded. Both experiments provided evidence for the presence of linear (n ≥ 2) and cyclic structures (n ≥ 3) which were predicted by ab initio calculations as comparably stable. The mass spectra clearly reflect a fundamentally different behaviour of the two types of clusters within the expansion zone: the linear species exhibit the cabability of cluster growth, while the cyclic ones do not. This leads to a characteristic size distribution with two marked maxima. During matrix deposition, considerable distortions of the clusters are created which may be healed out by annealing. The resulting sharp bands in the CH stretching region were assigned in agreement with ab initio calculations and previous IR studies aiming at small linear and cyclic species (n ≤ 3) in diverse liquid and solid environments.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

HCN Clusters in Molecular Beams and Cryogenic Matrices

Beichert

Pfeiler

Knözinger

1995

Ber Bunsenges Phys Chem

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“…Experimental cooling methods suited for the purpose include supersonic adiabatic expansion into vacuum, collisional cooling, and matrix isolation. 14,15 This latter method differs from the two former ones in that the solid matrix of ͑usually͒ argon strongly interacts with both the monomers and the clusters, rendering statements about the bare molecules and clusters difficult. Considered to be the more elegant, adiabatic jet expansion 1,16 is used much more frequently than collision cooling.…”

Section: Introductionmentioning

confidence: 99%

Liquid-helium temperature long-path infrared spectroscopy of molecular clusters and supercooled molecules

Bauerecker

Weitkamp

et al. 2001

Review of Scientific Instruments

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Collisional cooling and supersonic jet expansion both allow us to perform infrared spectroscopy of supercooled molecules and atomic and molecular clusters. Collisional cooling has the advantage of higher sensitivity per molecule and enables working in thermal equilibrium. A new powerful method of collisional cooling is presented in this article. It is based on a cooling cell with integrated temperature-invariant White optics and pulsed or continuous sample-gas inlet. The system can be cooled with liquid nitrogen or liquid helium and operated at gas pressures between <10−5 and 13 bar. Temperatures range from 4.2 to 400 K and can be adjusted to an accuracy of ±0.2 K over most of the useable range. A three-zone heating design allows homogeneous or inhomogeneous temperature distributions. Optical path lengths can be selected up to values of 20 m for Fourier transform infrared (FTIR) and 40 m for laser operation. The cell axis is vertical, so optical windows are at room temperature. Diffusive trapping shields and low-power electric heating keep the mirrors free from perturbing deposits. The cell can be operated in a dynamic buffer-gas flow-cooling mode. A comprehensive review of existing collisional cooling cells is given. The formation of CO clusters from the gas phase was investigated using FTIR spectroscopy. For the isotope mixture consisting of C1613O,13C18O, and C1612O, a conspicuous change in the main spectroscopic structure of the clusters was observed between 20 and 5 K. The cluster bandwidth of the main isotope C1613O triples. This behavior could be interpreted as a change from the crystalline to the amorphous state or as a decrease in size to smaller clusters with relatively larger surfaces. To our knowledge, this is the first IR investigation of molecular clusters obtained by collisional cooling in this temperature range. For CO2 the change from the monomer to crystalline clusters was investigated. The observed spectra vary considerably with temperature. FTIR spectra of CO2 clusters observed previously by other researchers could be reproduced. The system allows us to determine various gases with a FTIR detection limit in the lower ppb range. With these concentrations and at temperatures <10 K the monomers can be supercooled, and small clusters can be obtained.

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“…Such a matrix effect was observed for CO 2 in an argon matrix in various studies . The infrared (IR) spectrum of CO 2 trapped in argon reveals multiple peaks in the range of the antisymmetric stretching and the bending vibrations, which are dependent on the CO 2 ‐rare gas ratio, the deposition time and annealing temperature.…”

Section: Introductionmentioning

confidence: 66%

“…The infrared (IR) spectrum of CO 2 trapped in argon reveals multiple peaks in the range of the antisymmetric stretching and the bending vibrations, which are dependent on the CO 2 ‐rare gas ratio, the deposition time and annealing temperature. Initially, the studies tried to assign the various signals to CO 2 monomers and dimers . The more recent studies, however, tried to avoid the CO 2 dimer formation by using highly dilute matrices and low temperatures .…”

Section: Introductionmentioning

confidence: 99%

A Validation of Cluster Modeling in the Description of Matrix Isolation Spectroscopy

2019

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Matrix isolation is a fundamental tool for the synthesis and characterization of highly reactive novel species and investigation of unusual bonding situations. Ab initio descriptions of guest-host interactions in matrix isolation are highly demanding, as the weak interactions between guest and host can influence the former's oftentimes challenging electronic structure. In this study, the matrix effects on a single CO 2 molecule in an argon matrix were investigated with dispersion-corrected density functional theory calculations. Three different guest-host structures were described by bulk models employing periodic boundary conditions as well as cluster models. The calculations were analyzed with respect to structural features of the CO 2 molecule and its immediate surroundings. Also, the molecule's harmonic frequencies were determined. The calculated frequencies were in qualitative agreement with experimental observations. The cluster models produced comparable results given that the clusters were large enough to reproduce the structural features of the bulk model.

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Matrix isolation studies of CO2 clusters emerging from adiabatic expansion

Cited by 27 publications

References 4 publications

HCN Clusters in Molecular Beams and Cryogenic Matrices

HCN Clusters in Molecular Beams and Cryogenic Matrices

Liquid-helium temperature long-path infrared spectroscopy of molecular clusters and supercooled molecules

A Validation of Cluster Modeling in the Description of Matrix Isolation Spectroscopy

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