Vibrational spectroscopy of the borate mineral pinnoite MgB2O(OH)6

There is a large number of boron containing minerals with water and/or hydroxyl units of which pinnoite MgB2O(OH)6 is one. Some discussion about the molecular structure of pinnoite exists in the literature. Whether water is involved in the structure is ill-determined. The molecular structure of pinnoite has been assessed by the combination of Raman and infrared spectroscopy. The Raman spectrum is characterized by an intense band at 900 cm−1 assigned to the BO stretching vibrational mode. A series of bands in the 1000–1320 cm−1 spectral range are attributed to BO antisymmetric stretching modes and in-plane bending modes. The infrared spectrum shows complexity in this spectral range. Multiple Raman OH stretching vibrations are found at 3179, 3399, 3554 and 3579 cm−1. The infrared spectrum shows a series of overlapping bands with bands identified at 3123, 3202, 3299, 3414, 3513 and 3594 cm−1. By using a Libowitzky type function, hydrogen bond distances were calculated. Two types of hydrogen bonds were identified based upon the hydrogen bond distance. It is important to understand the structure of pinnoite in order to form nanomaterials based upon the pinnoite structure.

Vibrational spectroscopy of the borate mineral tunellite SrB6O9(OH)2·3(H2O) : implications for the molecular structure

Tunellite is a strontium borate mineral with formula: SrB6O9(OH)2∙3(H2O) and occurs as colorless crystals in the monoclinic pyramidal crystal system. An intense Raman band at 994 cm-1 was assigned to the BO stretching vibration of the B2O3 units. Raman bands at 1043, 1063, 1082 and 1113 cm-1 are attributed to the in-plane bending vibrations of trigonal boron. Sharp Raman bands observed at 464, 480, 523, 568 and 639 cm-1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3567 and 3614 cm-1, attributed to OH units. The molecular structure of a natural tunellite has been assessed by using vibrational spectroscopy.

Vibrational spectroscopy of the copper (II) disodium sulphate dihydrate mineral kröhnkite Na2Cu(SO4)2 · 2H2O

A natural single-crystal specimen of the kröhnkite from Chuquicamata, Chile, with the general formula Na2Cu(SO4)2 · 2H2O, was investigated by Raman and infrared spectroscopy. The mineral kröhnkite is found in many parts of the world's arid areas. Kröhnkite crystallizes in the monoclinic crystal system with point group 2/m and space group P21/c. It is an uncommon secondary mineral formed in the oxidized zone of copper deposits, typically in very arid climates. The Raman spectrum of kröhnkite dominated by a very sharp intense band at 992 cm−1 is assigned to the ν1 symmetric stretching mode and Raman bands at 1046, 1049, 1138, 1164, and 1177 cm−1 are assigned to the ν3 antisymmetric stretching vibrations. The infrared spectrum shows an intense band at 992 cm−1. The Raman bands at 569, 582, 612, 634, 642, 655, and 660 cm−1 are assigned to the ν4 bending modes. Three Raman bands observed at 429, 445, and 463 cm−1 are attributed to the ν2 bending modes. The observation that three or four bands are seen in the ν4 region of kröhnkite is attributed to the reduction of symmetry to C2v or less.

Polarized infrared absorption spectrum of matrix-isolated methylperoxyl radicals, CH3OO (X)over-tilde 2A ''

We have used a tandem pair of supersonic nozzles to produce clean samples of CH3OO radicals in cryogenic matrices. One hyperthermal nozzle decomposes azomethane (CH3NNCH3) to generate intense pulses of CH3 radicals, While the second nozzle alternately fires a burst Of O-2/Ar at the 20 K matrix. The CH3/O-2/20 K argon radical sandwich acts to produce target methylperoxyl radicals: CH3 + O-2 --> CH3OO. The absorption spectra of the radicals are monitored with a Fourier transform infrared spectrometer. We report 10 of the 12 fundamental infrared bands of the methylperoxyl radical CH3OO, (X) over tilde (2)A", in an argon matrix at 20 K. The experimental frequencies (cm(-1)) and polarizations follow: the a' modes are 3032, 2957, 1448, 1410, 1180, 1109, 90, 492, while the a" modes are 3024 and 1434. We cannot detect the asymmetric CH3 rocking mode, nu(11), nor the torsion, nu(12). The infrared spectra of (CH3OO)-O-18-O-18, (CH3OO)-C-13, and CD3OO have been measured as well in order to determine the isotopic shifts. The experimental frequencies, {nu}, for the methylperoxyl radicals are compared to harmonic frequencies, {omega}, resulting from a UB3LYP/6-311G(d,p) electronic structure calculation. Linear dichroism spectra were measured with photooriented radical samples in order to establish the experimental polarizations of most vibrational bands. The methylperoxyl radical matrix frequencies listed above are within +/-2% of the gas-phase vibrational frequencies. A final set of vibrational frequencies for the H radical, are recommended. See also http://ellison.colorado.edu/methylperoxyl.

The vibration spectrum of rutile

The long-wave lattice dynamics of rutile has been studied using a rigid ion model. The vibration frequencies for the zero wavevector have been calculated using the expressions for the frequencies of the normal modes derived group theoretically. The observed Raman and infrared frequencies have been explained.

Raman spectrum of crystalline aminosulphonic acid

The Raman spectrum of a single crystal of sulphamic acid has been recorded withλ 2537 excitation. Thirty-eight lines have been observed, of which twenty-nine have been recorded for the first time. Seven Raman lines with shifts in the region 50–155 cm.−1 have been assigned to the lattice oscillations, two at 177 and 240 cm.−1 have been attributed to the low-frequency hydrogen bond vibrations.. The splitting of the degenerate modes and the appearance of N-H....O bonded stretching vibrations are consistent with the structural data which expect the presence of the free molecule as a Zwitter ion with only slight distortion from C3v symmetry.

Raman spectrum of crystalline cadmium acetate dihydrate

The Raman spectrum of a single crystal of cadmium acetate dihydrate has been recorded for the first time using λ 2537 excitation. Twenty-three lines have been observed out of which ten have been attributed to the internal oscillations of the acetate ion, nine to the lattice modes, two to low-frequency hydrogen bond vibrations. A line at 308 cm.−1 and the continuum 3250–3560 cm.−1 have been assigned to the Cd-O6 and internal vibrations of the water molecules.

Raman spectrum of diglycine barium chloride monohydrate

The Raman spectrum of diglycine barium chloride monohydrate in the single crystal form has been recorded using λ 2536·5 excitation. 43 Raman lines (9 lattice and 34 internal) have been recorded. Satisfactory assignments have been given for most of the observed Raman lines. It is concluded from a comparison of the Raman spectrum of this compound with those of glycine and of other addition compounds of glycine, that the glycine unit exists in the zwitterion form in the structure of diglycine barium chloride monohydrate.

Raman spectrum of triglycine selenate (G3Se), [(NH2CH2COOH)3 H2SeO4]

The Raman spectrum of a single crystal of triglycine selenate G3Se which is ferroelectric below 22° C. has been photographed using λ 2537 excitation. 42 Raman lines have been recorded of which 6 belong to the lattice spectrum, 3 are due to NH...O oscillations and the remaining 33 are due to internal oscillations of the ions of glycine and SeO4--. There is a close similarity between the spectrum of triglycine selenate and the spectrum of its isomorph, triglycine sulphate, the frequency shifts due to the SO4-- ion being replaced by the frequency shifts due to the SeO4-- ion. The existence of glycine in the zwitterion form in the structure of G3Se is substantiated by the appearance in the Raman spectrum of lines which are attributable to NH3+ groups and COO- groups. The appearance of the additional C-H line at 2982 cm.-1 in the spectrum of triglycine selenate which is absent in the spectrum of α-glycine indicates the existence of planar monoprotonated glycine also in the structure, as indicated by X-ray studies.

Raman spectrum of lanthanum ethyl sulphate nonahydrate

Raman spectrum of a single crystal of lanthanum ethyl sulphate has been recorded for the first time using the λ 2537 radiation Forty-one lines have been identified out of which eight belong to the lattice oscillations, seven to the internal vibrations of the water molecule and the remaining twenty-six to the internal vibrations of the ethyl sulphate group. The Raman spectrum of ethyl sulphate (liquid) has also been recorded using the λ 4358 excitation and is compared with the spectrum of lanthanum ethyl sulphate. Thirty Raman lines could be identified in the spectrum of ethyl sulphate, of which fourteen are recorded for the first time. Probable assignments of the observed frequencies are also given. The sulphate group is found to have O-SO3 structure in lanthanum ethyl sulphate, while it has a co-ordination {Mathematical expression} in ethyl sulphate.

Vibrational analysis of the (B2P{cyrillic}→X2P{cyrillic}) system of NS

A few red degraded bands attributable to NS have been reported earlier by Fowler and Barker, Dressler and Barrow et al, and they occur in the same region (2300 to 2700 Å) as the bands of the known systems (C2∑+-X2P{cyrillic}) and (A2Δ-X2P{cyrillic}). Measurements made on the heads of some of these weak bands led Barrow et al. to believe that these bands may form a system analogous to the β-system of NO and be due to a2P{cyrillic}-2P{cyrillic} transition. The spectrum of NS has now been studied in a little more detail by means of an uncondensed discharge through dry nitrogen and sulphur vapour in the presence of argon and thirty three bands belonging to this system have been recorded in the region 2280 to 2760 Å. It has been found possible to represent the band heads by means of the equation {Mathematical expression}. Taking the lower state doublet interval as 223 cm-1, it is shown that the separation in the upper state is 94 cm-1. The ratio of the force constants in the upper and the ground states is found to be 0·39 and is nearly the same as that in the β-system of NO (0·30). The present vibrational analysis therefore supports the view that these new red degraded bands of NS arise from a (B2P{cyrillic}→X2P{cyrillic}) transition and the observed intensity distribution in the form of a wide parabola is also in qualitative agreement with what is expected from the moderately large Δ re (∼0·12Å) value.

The Raman spectrum of boric acid

The Raman spectrum of crystalline boric acid is recorded using mercuryλ2537 excitation. Fifteen Raman lines, three of them belonging to the lattice spectrum, are reported. Satisfactory assignments of all the observed Raman frequencies are made using the available X-ray crystal structure data. From the presence of a new high frequency Raman band at about 3420 cm.−1 it is suggested that there might be a small number of long, weak O-H....O hydrogen bonds in the crystal, in addition to the hydrogen bonds of moderate strength reported from X-ray diffraction data.

The emission spectrum of bismuth bromide (BiBr)-"A" system

The emission spectrum of bismuth monobromide has been investigated and a vibrational analysis of the A→X system has been made. About 286 bands were recorded in the region λλ 4595–6063 and the isotope effect due to Br79 and Br81 was observed in about 87 bands. A value of 2·74 ev. for the dissociation energy of the excited state has been obtained and arguments have been given to show that the dissociation products in the excited state are Bi(4S3/2) and Br(2P3/2) and that those of the ground state are most probably Bi (4S3/2) and Br (2P1/2) atoms.

Raman spectrum of l-asparagine monohydrate

The Raman spectrum of l-asparagine monohydrate in the form of a single crystal has been recorded for the first time. λ 2537 excitation has been used. Fifty-three Raman frequency shifts have been recorded. They are grouped as follows: Eight Raman lines coming under the lattice spectrum, three Raman lines arising from low-frequency vibrations of the hydrogen bonds and the remaining forty-two arising from the internal oscillations of the asparagine molecule. Appropriate assignments have been given for the observed Raman lines

Raman spectrum of strontium titanate

The Raman spectrum of strontium titanate has been recorded using λ 4358 of mercury as exciter. The observed spectrum consists of 7 Raman lines, one of which is of low frequency, as expected from the recent theory of Cochran. 6 of these Raman lines have been interpreted as the first order spectrum arising from a small deviation of the cubic strontium titanate from its idealized symmetry. It has been shown that one normal mode of SrTiO3 neglected by J.T. Last, will be really active in infrared absorption in the region of 440 cm-1 and that it has to be taken into account in the interpretation of the infrared spectra of titanates. The four vibrational modes of the unit cell of SrTiO3 correspond to frequencies of 90, 335, 441 and 620 cm-1 observed in Raman effect. The large width of the Raman lines and the additional lines at 256 cm-1 and 726 cm-1 have been attributed to a splitting of the longitudinal and transverse optical modes. With the observed frequencies it has been found possible to account for in a satisfactory manner the specific heat of SrTiO3 in the range 54·84° K to 1800° K.