Comprehensive high resolution study of the SiH(M=28,29,30) tetradecad stretching bands: Appearance and applications of the isotopic substitution effect in molecules of spherical symmetry.

A set of new relations between different spectroscopic parameters of the high symmetry XY spherical top molecules is derived on the basis of the general isotopic substitution theory, and a comprehensive high accurate analysis of the five stretching bands (the bands ν+ν(F), 2ν(F), 2ν(E), 2ν(A), and 2ν(A); the three latter ones are forbidden in absorption) of the tetradecad of the SiH molecule is made. The high resolution spectra of SiH(M=28,29,30) in their natural abundance were recorded with a Bruker IFS125 HR Fourier transform infrared spectrometer at the Technische Universität Braunschweig, Germany with an optical resolution of 0.003 cm and theoretically analyzed (in this case, for the first time both for all five bands of the SiH and SiH species, and for 2ν(E), 2ν(A) bands of the SiH one).

Improved Theory of the Effective Dipole Moments and Absolute Line Strengths of the XY Asymmetric Top Molecules in the Doublet Electronic States.

A new effective dipole moment model for the XY (C2v-symmetry) molecule in a doublet electronic state is derived that includes (as special cases) all currently known models of effective dipole moments for such types of molecules, and allows us to take into account the influence of spin-rotation interactions on the effective dipole moment operator that were not considered in the preceding studies. Necessary for the analysis of absolute line strengths, the matrix elements of this dipole moment operator are derived. A comparison with the previous analog models is made and discussed.

Effective Dipole Moment Model for Axially Symmetric Molecules: Application to the Precise Study of Absolute Line Strengths of the Fundamental of CHCl.

The effective dipole moment model for molecules of axial C3v symmetry is derived on the basis of the symmetry properties of a molecule which, on the one hand, is of the same order of efficiency (but much simpler and clearer in applications) as the analogous models derived on the basis of the irreducible tensorial sets theory, and, on the other hand, mathematically more correct in comparison with concepts like the Herman-Walles function used in the models. As an application of the general results obtained, we discuss high-resolution infrared spectra of CH335Cl, recorded with the Zürich prototype ZP2001 (Bruker IFS125 HR) Fourier transform infrared spectrometer at a resolution of 0.001 cm-1 and analyzed in the region of 880-1190 cm-1 (ν6 bending fundamental centered at ν0 = 1018.

High resolution spectroscopy of asymmetric top molecules in nonsinglet electronic states: the ν fundamental of chlorine dioxide (OClO) free radical in the XB electronic ground state.

Highly resolved spectra of the OClO isotopologue of chlorine dioxide were recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer in the region of the ν band. The analysis was made in the frame of the spin-rotational effective Hamiltonian (in A-reduction and I-representation) taking into account spin-rotational coupling operators up to the sixth order and the corresponding reduction of the Hamiltonian. The mathematical description of the ro-vibrational spectra was implemented to the specially created computer program ROVDES.

On the method and results of calculation of vibrational tetrahedral sub-level energies and resonance interactions in vibrational spectra of high symmetry molecules: CH and GeH as an application of the XY (T) molecule.

We report here the analytical description of one of the important problems in the study of XY (T) molecules, namely, description of vibrational tetrahedral sub-level structures and resonance interactions caused by the high symmetry of a molecule. The results obtained are applied to description of the vibrational energy spectrum of the CH and GeH molecules.

High-resolution spectroscopy of CHD: Line positions and energy structure of the strongly interacting ν,ν,ν,ν and ν bands.

High resolution infrared spectra of CHD were recorded in the region of 550-1950 cm with a Bruker IFS125 HR Fourier transform infrared spectrometers and rotational structures of the five lowest strongly interacting ν, ν,ν,ν and ν bands were analyzed. The number of about 28000 transitions (4200/6800/5600/5000/6400 for the bands ν,ν,ν,ν and ν) with J = 40 and K = 20 were assigned to these five bands. The weighted fit of 3990 upper energy values obtained from the experimentally recorded transitions was made with a Hamiltonian which takes into account resonance interactions between all studied bands as well as with the sixth ν band which was considered in this case as a "dark" one.

High resolution spectroscopy of the ν+ν band of the ClO free radical: Spin-rotation-vibration interactions.

The high resolution spectrum of the ν+ν band of the ClO free radical was recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer and theoretically analysed with an improved theoretical basis including the reduced effective spin-rotation Hamiltonian (which takes into account sixth order operators describing spin-rotational interactions) and a newly created computer code ROVDES for the ro-vibrational spectra of open-shell free radicals. About 2600 spin-ro-vibrational transitions with the values N=59 and K=17 (being about 2.4 times higher in comparison with the number of assigned transitions known in the literature) were assigned to the ν+ν band of ClO and 1049 spin-ro-vibrational energies (produced only from unblended non-saturated and not very weak experimental lines) of the (101) upper vibrational state were obtained.

High resolution ro-vibrational analysis of molecules in doublet electronic states: the fundamental of chlorine dioxide (OClO) in the electronic ground state.

We report the spectrum of the ν1 fundamental of chlorine dioxide centered in the infrared atmospheric window at 945.592 cm-1 measured with essentially Doppler limited resolution at an instrumental line width of 0.001 cm-1 using the Zürich prototype ZP2001 Bruker IFS 125 HR Fourier transform infrared spectrometer.

On the method of precise abundance determination of isotopologues in a gas mixture.

A method is presented which allows one to derive partial pressures of isotopologue molecules in a gaseous mixture under the conditions of rapid isotope exchange. For this purpose, isotopic relations between effective dipole moment parameters of a "parent" molecule and its related isotopically substituted species are derived on the basis of the general isotopic substitution theory. The efficiency of the method is illustrated.

Hypercooling Temperature of Water is about 100 K Higher than Calculated before.

For deeply supercooled liquids the transition from a two-stage freezing process to complete solidification in just one freezing step occurs at the hypercooling temperature, a term that seems to be almost unknown in water research; to our knowledge, it has only been mentioned by Dolan et al. for high-pressure ice. The reason for the absence of this expression may be that the best estimate to be found in the literature for the hypercooling temperature of water is about -160 °C (113 K).

A Non-Exploding Alkali Metal Drop on Water: From Blue Solvated Electrons to Bursting Molten Hydroxide.

Alkali metals in water are always at the brink of explosion. Herein, we show that this vigorous reaction can be kept in a non-exploding regime, revealing a fascinating richness of hitherto unexplored chemical processes. A combination of high-speed camera imaging and visible/near-infrared/infrared spectroscopy allowed us to catch and characterize the system at each stage of the reaction.

Critical Radius of Supercooled Water Droplets: On the Transition toward Dendritic Freezing.

The freezing of freely suspended supercooled water droplets with a diameter of bigger than a few micrometers splits into two rather different freezing stages. Within the first very fast dendritic freezing stage a spongy network ice with an ice portion of less than one-third forms and more than two-thirds of liquid water remain. In the present work the distribution of the ice portion in the droplet directly after the dendritic freezing phase as well as the evolution of the ice and temperature distribution has been investigated in dependence of the most relevant parameters as droplet diameter, dendritic freezing velocity (which correlates with the supercooling) and heat transfer coefficient to the surroundings (which correlates with the relative droplet velocity compared to the ambient air and with the droplet size).

Coulomb explosion during the early stages of the reaction of alkali metals with water.

Alkali metals can react explosively with water and it is textbook knowledge that this vigorous behaviour results from heat release, steam formation and ignition of the hydrogen gas that is produced. Here we suggest that the initial process enabling the alkali metal explosion in water is, however, of a completely different nature. High-speed camera imaging of liquid drops of a sodium/potassium alloy in water reveals submillisecond formation of metal spikes that protrude from the surface of the drop.

Survey of the high resolution infrared spectrum of methane ((12)CH4 and (13)CH4): partial vibrational assignment extended towards 12,000 cm(-1.).

We have recorded the complete infrared spectrum of methane (12)CH4 and its second most abundant isotopomer (13)CH4 extending from the fundamental range starting at 1000 cm(-1) up to the overtone region near 12,000 cm(-1) in the near infrared at the limit towards the visible range, at temperatures of about 80 K and also at 298 K with Doppler limited resolution in the gas phase by means of interferometric Fourier transform spectroscopy using the Bruker IFS 125 HR prototype (ZP 2001) of the ETH Zürich laboratory. This provides the so far most complete data set on methane spectra in this range at high resolution. In the present work we report in particular those results, where the partial rovibrational analysis allows for the direct assignment of pure (J = 0) vibrational levels including high excitation.

Electric effect during the fast dendritic freezing of supercooled water droplets.

An electrical phenomenon consisting of two alternating voltage peaks of up to 6 V amplitude was observed during the rapid dendritic freezing phase of supercooled water droplets in the millimeter size range with supercoolings ΔT in the range of 5 to 20 K. For correlation of the dendritic freezing front with the electric potential, a fast recording oscilloscope was combined with a high-speed camera operating at up to 5000 frames per second. The strength of the effect is roughly proportional to the supercooling and dendritic freezing speed.

High resolution spectroscopy and the first global analysis of the Tetradecad region of methane 12CH4.

We present the first detailed analysis of the infrared spectrum of methane (12)CH4 in the so-called Tetradecad region from 2.1 to 1.6 μm (4760-6250 cm(-1)).

Water ice nanoparticles: size and temperature effects on the mid-infrared spectrum.

Mid-infrared spectra have been measured for cubic ice (I(c)) nanoparticles (3-150 nm diameter) formed by rapid collisional cooling over a wide range of temperatures (5-209 K). Spectral diagnostics, such as the ratio of surface related dangling OH to interior H-bonded OH stretch bands, reveal the manner in which particle size depends on bath gas temperature and density, and on water molecule concentration. For particles smaller than 5 nm strained intermolecular bonds on the surface and subsurface cause the predominant OH stretch peak position to be dramatically blue shifted by up to 40 cm(-1).

Effect of nitrogen adsorption on the mid-infrared spectrum of water clusters.

Experimental Fourier-transform infrared spectra and DFT calculated infrared spectra are compared to investigate the effect of adsorbed nitrogen on the OH-stretch band complex of water clusters. Using a collisional cooling experiment, pure as well as partially and completely N(2)-covered water clusters consisting of 20-200 water molecules have been generated in thermal equilibrium in the aerosol phase within the temperature range of 5-80 K. Computational IR-spectra simulations have been performed for discrete pure and N(2)-covered water clusters including 10, 15, 20, and 30 water molecules.

IR spectroscopy of physical and chemical transformations in cold hydrogen chloride and ammonia aerosols.

Aerosol particles of hydrogen chloride corresponding to three distinct solid phases have been generated in a collisional cooling cell and observed via FTIR spectroscopy. The cubic phase of HCl was observed with cell temperatures of 90-100 K, while the highly ordered orthorhombic phase predominated below this temperature. The previously reported metastable phase was also observed under some conditions.

Infrared spectroscopy of ozone and hydrogen chloride aerosols.

Aerosols of ozone have been generated in a collisional cooling cell and observed over a small temperature range via FTIR spectroscopy, with the phase transition from the vapour taking place in the range 80-84 K. The condensed phase bands at 1038 cm(-1) (nu3) and 2105 cm(-1) (nu1+nu3) were assigned to the liquid phase. Aerosols were also generated from mixtures of ozone and HCl.

High-resolution near infrared spectroscopy and vibrational dynamics of dideuteromethane (CH2D2).

We report the infrared spectrum of CH(2)D(2) measured in the range from 2800 to 6600 cm(-1) with the Zurich high-resolution Fourier transform interferometer Bruker IFS 125 prototype (ZP 2001, with instrumental bandwidth less than 10(-3) cm(-1)) at 78 K in a collisional enclosive flow cooling cell used in the static mode. Precise experimental values (with uncertainties between 0.0001 and 0.

Infrared analysis of CO ice particles in the aerosol phase.

Fourier transform infrared extinction spectra of a variety of CO ice aerosols, generated at low temperatures in a liquid helium cooled collisional-cooling cell, have been analyzed. Different operation modes of the cooling system were used for the generation of spherical and nonspherical CO nanoparticles at temperatures between 5 and 35 K and with diameters between 10 and 1000 nm. In contrast to the predominantly amorphous CO films described in the literature the presented CO particles are (poly)crystalline.

Observation of a transition in the water-nanoparticle formation process at 167 K.

Rapid-scan Fourier transform infrared spectroscopy of the vapor/solid formation process of water nanoparticles in the 180-140 K temperature range at thermal-equilibrium conditions is reported. At 167 K a transition in the formation process was observed: the particle volume quintuples and the particle formation time triples within a temperature interval of +/-0.4 K caused by the temperature control.

Generation and characterization of surface layers on acoustically levitated drops.

Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops.

FTIR study of CO2 and H2O/CO2 nanoparticles and their temporal evolution at 80 K.

Fourier transform infrared (FTIR) spectroscopy combined with a long-path collisional cooling cell was used to investigate the temporal evolution of CO2 nanoparticles and binary H2O/CO2 nanocomposites in the aerosol phase at 80 K. The experimental conditions for the formation of different CO2 particle shapes as slab, shell, sphere, cube, and needle have been studied by comparison with calculated data from the literature. The H2O/CO2 nanoparticles were generated with a newly developed multiple-pulse injection technique and with the simpler flow-in technique.