Raman spectroscopy of formic acid and its dimers isolated in low temperature argon matrices

Olbert‐Majkut, Adriana; Ahokas, Jussi; Lundell, Jan; Pettersson, Mika

doi:10.1016/j.cplett.2008.12.011

Cited by 74 publications

(86 citation statements)

References 42 publications

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“…17,31 Upon annealing above 27 K, the bands of the trans-HCOOD monomer and tt5 dimer decrease in intensity and the bands of the tt1 and tt2 dimers grow ( Figure 2, trace 2), similar to the case of HCOOH. 17,20,27,31 Annealing at 34 K vanishes the tt5 band at 2506.4 cm −1 completely, indicating the conversion of tt5 to more stable trans−trans structures. The weak broad absorption at ca.…”

Section: ■ Experimental Detailsmentioning

confidence: 98%

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Dimers of the Higher-Energy Conformer of Formic Acid: Experimental Observation

et al. 2012

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We report on the first experimental observation of formic acid dimers composed of two molecules of the higher-energy cis conformer. The cis−cis formic acid dimers are prepared in an argon matrix by selective vibrational excitation of the ground state trans conformer (deuterated form HCOOD) combined with thermal annealing of the matrix at about 30 K. Five cis−cis formic acid dimers are predicted by ab initio calculations (interaction energies from −16.9 to −27.2 kJ mol −1 ), and these structures are used for the assignment of the experimental spectra. Selective vibrational excitation of the obtained cis−cis dimers leads to the formation of several trans−cis dimers, which supports the proposed assignments.

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Section: ■ Experimental Detailsmentioning

confidence: 98%

“…The trans−trans dimers have been extensively studied theoretically. 17−23 Several such dimers have been observed experimentally in the gas phase, 24−26 raregas matrices 17,20,27−31 and helium nanodroplets. 32 A number of mixed trans−cis dimeric structures were also predicted 17,23,33 and observed experimentally.…”

Section: ■ Introductionmentioning

confidence: 99%

Dimers of the Higher-Energy Conformer of Formic Acid: Experimental Observation

et al. 2012

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“…Raman measurements were performed using the backscattering geometry as described previously [20]. The excitation source was a solid-state diode-pumped laser (Verdi, Coherent) operating at 532.0 nm, and a power level up to 600 mW at the sample was used.…”

Section: Experimental Methodsmentioning

confidence: 99%

Librational motion of CO in solid Ar: Raman and IR spectra and quantum simulations

Olbert‐Majkut

Pettersson

Kiljunen

2012

Low Temperature Physics

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Rovibrational Raman spectra of CO molecules isolated in solid Ar were measured for the 9-30 K temperature range and compared to past and present IR spectra. The fundamental band appears as a triplet-split structure, where the center peak shows completely different response to temperature in the Raman and IR spectroscopies. The peak is sharp and stable in Raman but reversibly broadens beyond recognition in IR upon annealing. The red-shifted, intense line of the triplet is found thermally inert similarly in both spectroscopies. The third line is the weakest, and as concentration dependent, it is assigned to a dimer as before. The CO-H 2 O impurity complex is identified as a side band. We employ crystal field and quantum chemical modeling to interpret the disparity between the spectroscopies. The stable and broadening lines are given assignments to double-and singlesubstitution sites, respectively. Thermal excitations are not effective in the former case of angularly tightconfined, deep potential well. In the single-substitutional case, the librational level structure shows up in discriminating between the Raman and IR selection rules. An effectively ΔJ = 0 totally symmetric transition is found for Raman that is uncoupled from lattice phonons and corresponding broadening mechanisms. The low-temperature limit necessitates the use of a fixed lattice approach while the warmer end of the range is best described with an adiabatic, pseudorotating lattice approach. PACS

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“…Very recently, matrix isolation also became possible for Raman probing. 48 The spectral simplification offered by this technique comes at the price of matrix shifts, which are sometimes difficult to predict and can lead to changes in resonance patterns. 47 Therefore, more effort has been invested in infrared supersonic jet approaches over the last decade.…”

Section: Introductionmentioning

confidence: 99%

Probing the stiffness of the simplest double hydrogen bond: The symmetric hydrogen bond modes of jet-cooled formic acid dimer

Xue

Suhm

2009

The Journal of Chemical Physics

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Formic acid dimer is held together and kept planar by two strong hydrogen bonds, which give rise to intermolecular vibrations. Raman active fundamentals, overtones, and combination bands involving out-of-plane bending and stretching vibrations of the hydrogen bonds are recorded under jet-cooled, vacuum-isolated conditions between 100 and 750 cm−1 and assigned with the help of isotope substitution. Individual anharmonicity effects are shown to be very small (xi,j=−(1±2) cm−1), where they are accessible by experiment. However, they may accumulate to substantial differences between harmonic and anharmonic fundamental excitations. Preliminary experimental evidence for the most elusive fundamental vibration of formic acid dimer, symmetric OH torsion, is presented. A rigorous experimental reference frame for existing and future high level quantum chemical and dynamical treatments of this important prototype system is provided. The effects of clustering beyond the dimer on the low frequency dynamics are found to be small, whereas argon coating gives rise to blueshifts.

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Raman spectroscopy of formic acid and its dimers isolated in low temperature argon matrices

Cited by 74 publications

References 42 publications

Dimers of the Higher-Energy Conformer of Formic Acid: Experimental Observation

Dimers of the Higher-Energy Conformer of Formic Acid: Experimental Observation

Librational motion of CO in solid Ar: Raman and IR spectra and quantum simulations

Probing the stiffness of the simplest double hydrogen bond: The symmetric hydrogen bond modes of jet-cooled formic acid dimer

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