Lithium Formate Research Articles

Growth kinetics of lithium formate crystals in normal and heavy water solutions

Data on growth rates of hydrated lithium formate (LFM) and deuterated lithium formate (DLFM) crystal faces as a function of supersaturation at 307.65 K and observations of growth hillocks and liquid inclusions are presented and discussed. Following Bennema's modification of the BCF surface diffusion model as applied to crystal growth from solution, the values of growth parameters have been calculated and compared with the values reported for the growth of other substances. It was found that large liquid inclusions begin to appear at supersaturations σ > 0.0185 for LFM and σ > 0.0192 for DLFM, but tiny inclusions appear even at σ=0.0108.

The electrostatic term in lattice-energy calculations for lithium formate monodeuterate: determination from the experimental electron density

The electrostatic energy of crystalline LiCHO2.D2O has been calculated with three sets of net atomic charges. These sets have been obtained from ab initio and extended Hückel calculations as well as by the method of Tsirel'son & Ozerov [Soy. Phys. Crystallogr. (1979), 24, 662-666] from the X-ray electron density. It is shown that only the 'experimental' set of net atomic charges provides good agreement with the experimental evaluation of the lattice energy for LiCHO2. D2O.

A3Π and b3Σ–excited states of the so radical. Part 2.—Lifetimes of vibrational levels of the A state and quenching rates

A novel frequency-doubled, scanning dye laser has been used to excite individual ro-vibrational levels of the excited A3Π state of the SO free radical. The vibrational level range 6 v′ 0 has been studied, using pulses at excitation wavelengths between 246 and 262 nm, provided from a lithium formate monohydrate frequency-doubling crystal. The rotationally resolved laser-excitation spectrum of the 5–0 band of SO (A3Π–X3Σ–) is reported.Collision-free lifetimes were determined, giving radiative lifetimes τR/µs (1σ) for SO (A, v′) as follows: 9.8 ± 0.8, v′= 6; 9.3 ± 1.0, v′= 5; 10.4 ± 0.8, v′= 4; 11.5 ± 1.3, v′= 3; 14.1 ± 1.1, v′= 2; 17.9 ± 1.4, v′= 1; and 35.9 ± 2.6, v′= 0. No dependence of τR upon rotational (J′) or spin–orbit (Ω) quantum number in the excited-state manifold was found. However, the results showed a strong trend for τR to decrease, and for the electric dipole moment |Re|2 to increase, as a function of increasing vibrational quantum number v′, for the A3Π–X3Σ– transition of SO. Possible reasons for these results are considered.Rate constants for electronic quenching, kQ, were determined for several collision partners, following excitation of SO (A3Π1), v′= 5, N′= 6, 7 (c-component of A-doublet). For O2 and CS2 as collision partners, excitation of the d-components of N′= 8 and 9 also was studied, but gave the same results as the blended N′= 6, 7 (c-) states. Mean values of kQ(2σ, cm3 molecule–1 s–1) at 298 K were as follows: (5.2 ± 0.4)× 10–10, Q = CS2; (1.0 ± 0.2)× 10–10, Q = O2; (9 ± 1)× 10–12, Q = N2; (7.5 ± 1)× 10–12, Q = Ar; and (2.6 ± 0.5)× 10–11, Q = SF6.

Investigation of dispersion of the intensity of Raman light scattering by polaritons

An experimental investigation was made of Raman light scattering by polaritons as a function of their frequency in lithium iodate and lithium formate crystals. The spectra were recorded and the intensity was measured using an optical multichannel analyzer connected to a minicomputer in an pptical system of the kind employed earlier in the photographic technique. Dispersion of the nonlinear susceptibility of an LiIO3 crystal was determined near the 769 cm−1 lattice vibration. The results were compared with calculations based on the cross sections for Raman light scattering by transverse optical phonons, electrooptic constants, and second harmonic generation.

Low wavenumber Raman bands (300-25 cm −1) and isotope effects for eight isotopically substituted lithium formate monohydrates LiX′CO 2·X″ 2O

The Raman spectra of eight isotopically substituted lithium formate monohydrates, LiX′CO 2·X″ 2O, were investigated in the wavenumber region from 300 to 25 cm −1. The observed spectral data were assigned to the X′CO − 2 and X″ 2O lattice modes and discussed taking the isotope effects on the fundamental bands into account.

The generation of tunable UV radiation from 238–249 nm, by intracavity frequency doubling of a coumarin 102 dye laser

Lithium formate monohydrate has been used for intracavity frequency doubling of a coumarin 102 dye laser. The tuning range is 238–249 nm, with maximum generated UV powers 70 μW at 244 nm.

A study of sintering and magnetic parameters of spinel lithium ferrite; I. Pure lithium ferrite

Powdery spinel lithium ferrite, Li 0.5Fe 2.5O 4, was prepared from a mixture of complex ferric formate and lithium formate at different temperatures ranging from 300 to 700°C. The largest specific surface areas were established with samples obtained at 500°C. The highest density, reaching 98% of the theoretical lithium ferrite density, was found with the same samples on sintering at 1100°C. Some magnetic parameters of the high-density samples were measured.

Precision measurement of the1SLamb shift and of the1S−2Sisotope shift of hydrogen and deuterium

A precision measurement of the $1S$ Lamb shift of atomic hydrogen and deuterium, using high-resolution laser spectroscopy is reported. The $1S\ensuremath{-}2S$ transition was observed by Doppler-free two-photon spectroscopy, using a single-frequency cw dye laser near 4860 \AA{} with a nitrogen-pumped pulsed dye amplifier and a lithium formate frequency doubler. The $n=2\ensuremath{-}4$ Balmer-$\ensuremath{\beta}$ line was simultaneously recorded with the fundamental cw dye-laser output in a low-pressure glow discharge, using sensitive laser polarization spectroscopy. From a comparison of the two energy intervals a ground-state Lamb shift of 8151\ifmmode\pm\else\textpm\fi{}30 MHz has been determined for hydrogen and 8177\ifmmode\pm\else\textpm\fi{}30 MHz for deuterium, in agreement with theory. The same experiments yield a tenfold improved value of the $1S\ensuremath{-}2S$ isotope shift 670992.3\ifmmode\pm\else\textpm\fi{}6.3 MHz and provide the first experimental confirmation of the relativistic nuclear recoil contribution to hydrogenic energy levels.

Conical refraction in second harmonic generation in a crystal of lithium formate

Conical refraction in second harmonic generation in a crystal of lithium formate

The Role of Dislocations in the Thermal Dehydration of Lithium Formate Monohydrate

Abstract The kinetics of Lithium Formate Monohydrate (LFM) dehydration (single crystal samples) has been investigated at constant temperature (317 < T < 353) under dynamic vacuum both optically and thermogravimetrically. The process takes place with an induction period followed by a constant rate period. The first one is characterized by a surface nucleation which occurs mostly in connection with dislocations emerging on the (021), (110) and (010) faces and at the vertex-intersections of these planes; the second one corresponds to the advancement of a reaction interface (formed on the planes with l ≠ 0) along the c-axis. This topochemical model has been interpreted on the basis of the different features of the actual dislocations and of the reticular geometry of the LFM crystal.

Optical distortion in nonlinear phase conjugation by three-wave mixing

The phase and amplitude of a conjugate wave front generated by three-wave mixing in a lithium formate crystal were examined experimentally using a polarization shearing interferometer and a silicon diode array. It was found that the phase of the conjugate wave front had little distortion, while its amplitude was modulated significantly. The distortion is due to interference of conjugate waves generated from different positions in the crystal and not due to failure to satisfy the phase-matching requirement. A theoretical description is presented that is in good agreement with observation.

Automatic phase-matched frequency-doubling system for the 240–350-nm region

An automatic frequency-doubling system has been constructed using a lithium formate monohydrate crystal as the frequency doubler in a stationary optical arrangement. Without any readjustment of the crystal orientation, smooth tuning of the uv light over the 240-350-nm range has been obtained. The feasibility of this system for uv absorption measurements has been successfully demonstrated using S0(2) gas.

X–Nand multipole deformation electron density maps for the non-centrosymmetric structure lithium formate monohydrate, LiHCOO.H2O

Room temperature X - N difference electron density maps are calculated for the non-centrosymmetric lithium formate monohydrate, a potential ferroelectric, by taking the phases appropriate to Fo,x as those calculated from a multipole deformation density refinement [Hirshfeld (1971). Acta Cryst. B27, 769-781 ]. Both X - N and multipole deformation density maps are presented, and compared with earlier X - N maps derived using less rigorous procedures.

Lithium formate monohydrate: a comparison of the X–N difference density and structural parameters derived from different experiments

Lithium formate monohydrate: a comparison of the <i>X</i>–<i>N</i> difference density and structural parameters derived from different experiments

Optical phase conjugation in a lithium formate crystal

Optical phase reversal has been demonstrated using type-II phase matching in lithium formate operated as a degenerate optical parametric amplifier with pump peak powers as low as 103 W. The amplifier was driven in a collimated geometry.

Temperature‐dependent Raman study of H‐bonds and possible phase‐transition in LiHCOO·H2O

AbstractPolarized Raman spectra of single crystals of lithium formate monohydrate (LiHCOO·H2O) have been measured from 4.2 K to 320 K. In the high‐frequency region, the observed modes have been assigned and the water molecule vibrations identified. The crystallographic distances between the two oxygens involved in the two hydrogen bonds have been obtained from the frequencies of the stretching OH vibrations, and the corresponding O…︁O vibration frequencies have been predicted and identified in the low‐frequency region. Although the crystal is thought to be potentially ferroelectric, we have observed no evidence of any structural change or presence of a ‘soft’ phonon in the crystal in the temperature range studied. Our measurements in various configurations do not indicate the presence of any LOTO splittings or any hydrogen disorder in the crystal.

Picosecond source of coherent optical radiation tunable in the 350–680 nm range

Mixing of picosecond neodymium laser pulses of λ =1.06 μ. wavelength and 1 GW power with a continuous spectrum in lithium iodate and formate crystals produced tunable coherent radiation in the wavelength range 350–680 nm. The continuous spectrum was excited in the active element of an oscillator (with a neodymium glass rod) by high-power picosecond pulses produced by the oscillator itself. The tuning was based on the angular dispersion of the phase matching in the two crystals employed.

The influence of elastic anisotropy on the X-ray topographic image width of pure screw dislocations

The X-ray topographic image widths of pure screw dislocation lines along twofold axes of orthorhombic ammonium hydrogen oxalate hemihydrate, lithium formate monohydrate, thiourea and monoclinic potassium hydrogen oxalate have been studied. The widths observed on topographs made with imaging planes perpendicular to the dislocation line vary with the orientation of the incidence plane. This effect results from the elastic anisotropy, which gives rise to a varying slope of the helical surface formed by the distorted lattice planes. The displacements, strains, and effective misorientations of the imaging planes are quantitatively analysed for screw dislocations along a twofold axis or perpendicular to a mirror plane, taking into account elastic anisotropy. The image widths for various orientations of the incidence plane are calculated. The ratio of maximum and minimum widths is Wmax/Wmin = c44/c55, with c44 and c55 the maximum and minimum shear resistance, respectively, in the plane perpendicular to the dislocation line. Observed and calculated ratios are in good agreement.

Third-harmonic generation of Nd: YAG laser in lithium formate monohydrate

Third-harmonic generation of Nd: YAG laser in lithium formate monohydrate

Calculation of nonlinear optical coefficients for lithium formate monohydrate, using MINDO/3

MINDO/3 has been used to calculate the nonlinear optical coefficients for orthorhombic lithium formate monohydrate. The numerical agreement with experiment is reasonable but the calculated and observed coefficients differ in one sign relation.