The near ultraviolet absorption spectra ofortho- andmeta-thiocresols

The absorption spectra ofortho- andmeta-thiocresols have been studied in the present investigation. The ortho-thiocresol spectrum consists of about forty-five bands of rather a diffuse nature and in general low intensity in the region from 2873 Å to 2600 Å. The maximum number of bands is obtained by using a path length of 330 cm. for absorption, the temperature of the bulb being maintained at 14°C. Several of these bands are assigned as due tov-v-transitions. The (0, 0) band is chosen at 35386 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 729, 957 and 1159 and combinations and overtones of these are present. Themeta-thiocresol spectrum consists of about forty bands of rather a diffuse nature and very weak intensities in the region from 2900 Å to 2590 Å. The maximum number of bands is obtained by using a path length 200 cm. for absorption and by keeping the temperature of the bulb at 20° C. The (0, 0) band is chosen to be that at 34793 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 492, 611, 720, 845, 965, 1016 and 1155 cm.^?1 and combinations and overtones of these are present.     

The near ultraviolet absorption spectrum ofpara-thio-cresol

The absorption spectrum ofpara-thio-cresol consists of about ten bands in the region 2922 to 2600 Å. The bands are quite intense but broad and fail to show any structure such as is observed in the case ofpara-cresol bands. The maximum number of bands about ten is obtained by using an absorption path length of 100 cm. The (0, 0) band is chosen to be that at 34222 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 353, 752 and 1114 and combinations and overtones of these are found to be present.     

Floral colours and their origins

A new orientation is given to the subject of floral colours by the author’s discovery that these colours may be placed into two distinct spectral categories, which have been designated by him respectively as the spectrum of florachrome A and of florachrome B. Typical of these two categories are the colours ofDelphinium ajacis (larkspur) in the blue and pink varieties respectively, the former showing the spectrum of florachrome A and the latter that of florachrome B. As a general rule, all blue flowers exhibit the spectrum of florachrome A which consists of three distinct and clearly separated bands of absorption appearing respectively in the red at 630 mμ, in the yellow at 580 mμ and in the green at 540 mμ. The spectrum of florachrome B also consists of three distinct bands of absorption, but these now appear in the orange-yellow at 590 mμ, in the green at 545 mμ and in the blue-green at 505 mμ. Spectra exhibiting these features are reproduced with the paper. Their explanation is discussed and it is shown that they owe their origin to an electronic absorption frequency located at the first of the three bands combining with vibrational transitions, the oscillator being the CO group present in the structure of the florachrome.     

The near ultraviolet emission spectrum of tetralin (tetrahydronaphthalene)

An emission spectrum of tetralin (tetrahydronaphthalene) in the near ultraviolet excited by a transformer discharge through flowing vapour has been studied and about twenty-nine bands in emission have been photographed and measured on suitable instruments. Vibrational analysis of the bands in terms of the fundamental frequencies of the molecule is proposed and is compared with those obtained in the corresponding absorption spectrum of tetrahydronaphthalene studied by the author.² The results afford further confirmation of the correctness of the analysis and particularly the assignment of the (0,0) band proposed in the absorption spectrum of the molecule.     

Resonance phenomena in a semi-infinite string with a periodic end

We study the propagation of linear waves, generated by a compactly supported time-harmonic force distribution, in a semi-infinite string under the assumption that the material properties depend p-period-ically on the space variable outside a sufficiently large interval [0, a]. The spectrum of the self-adjoint extension A of the spatial part of the differential operator consists of a finite or countable number of bands and a (possibly empty) discrete set of eigenvalues located in the gaps of the continuous spectrum. We show that resonances of order t or t^½, respectively, occur if either ω² is an eigenvalue of A or (i) ω² is a boundary point of the continuous spectrum of A and (ii) the corresponding time-independent homogeneous problem has a non-trivial solution which is p-periodic or p-semiperiodic for x > a (‘standing wave’).     

Rotational analysis of the C2Σ+ — X2Σ+ system of AlO

The 2-0, 1-0, 0-0 and 0-1 bands of the C²Σ⁺-X²Σ⁺ system of AlO, lying at 2391.88 Å, 2438.35 Å, 2487.32 Å and 2548.51 Å respectively were excited in a low pressure arc and photographed on a 6.6-metre concave grating spectrograph in the third order at a dispersion of 0.37 Å/mm. From the rotational analysis of these bands, the following constants have been determined: B_e′ = 0.565₃ cm.^?1 a_e′ = 0.004₈ cm.^?1 T_e =40267.0 cm.^?1 B_e″ = 0.641₃ cm.^?1 a_{″ = 0.005 7} cm.^?1     

Raman and infrared spectra of ammonium selenate and lithium ammonium selenate

The Raman and infrared absorption spectra of (NH₄)₂ SeO₄, (ND₄)₂ SeO₄ and Li (NH₄) SeO₄ have been recorded at 300° K; while the spectra of the non-deuterated compounds have been recorded at 110° K also. (NH₄)₂ Se0₄ crystal exhibits 33 Raman lines, while LiNH₄SaO₄ shows 30 Raman lines at 300° K. Proper assignments have been given to the observed vibration frequencies. The SeO₄ ^?? ions and the (NH₄)⁺ ions are found to be highly distorted in these selenates. There is lowering of the N-H vibration frequencies due to hydrogen bonding. The present spectroscopic investigations do not reveal the existence of any phase transition in these selenates in the temperature region investigated.     

Emission spectrum of bromine excited in the presence of argon—part I

Bromine was excited by an uncondensed transformer discharge in the presence of argon. The spectrum obtained was found to be different from what one gets without the presence of a foreign gas and consists of (1) a short discrete band system in the region 3150–2970 Å, (2) an extensive discrete band system in the region 2950–2670 Å, (3) a short and weak discrete system in the region 2660–2590 Å and a set of diffuse bands in the region 3340–3190 Å. The wavelengths and wave numbers of the band heads of the system 2950–2670 Å, as obtained from the measurements of the plates taken on the first order 21-ft. grating spectrograph, are given along with the vibrational analysis. This system is shown to be due to a transition from an upper electronic state at 51802 cm.^-1 with ω′_e = 150·5 cm.^-1 and ω′_e X′_e = 1·15 cm.^-1 to the well known³ II _α (O₂ ⁺) state at 15918 cm.^-1     

Isotropic background cosmic X-rays in the energy range 50–290 KeV

The observations of omnidirectional X-ray flux at the top of the atmosphere have been extended upto 200 KeV using a balloon-borne NaI (Tl) scintillator detector at Hyderabad, India. The omnidirectional flux at 60 KeV is found to be 0·0066±0·0014 photons/cm.² sec. ster. KeV. The X-ray flux in the energy range 50–290 KeV can be adequately represented by the spectrum Ke^?2.2±0.4. New upper limits to the hard X-ray flux from the quiet sun have also been obtained from the same measurement.     

Numerical analysis for phase field simulations of moving interfaces with topological changes

Phase field methods are a widely accepted tool for the approximation of moving free interfaces in sharp interface problems. Topological changes in the solution, such as nucleation or vanishing of particles or merging or pinching of interfaces, lead to singularities in the free boundary. In the sharp interface model, these singularities cause both numerical and theoretical problems, whereas they are handled “automatically” in phase field simulations. Phase field models contain a length scale ε > 0 that vanishes in the sharp interface limit. Therefore, when ε → 0, practical numerical methods have to be robust in the sense that error estimates may only depend polynomially on ε^-1, not exponentially. We show that robust error control is possible past the occurrence of topological changes and without restrictive assumptions on the initial data. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical absorption spectrum of Ni2+ in Garnierite

The results obtained in the study of the absorption spectrum of Ni²⁺ in two samples of Garnierite are described. Both the samples of Garnierite have been studied by preparing their mineral oil mulls. One of these samples could however be studied in its crystal form as well. From the observed features, the absorption bands in both the samples of Garnierite have been attributed to an ion of Ni²⁺ in tetrahedral symmetry. The observed and calculated energies for the bands are found to be in close agreement with one another justifying the assumption that the site symmetry of Ni²⁺ ion is tetrahedral. For one of the Garnierite samples both the crystal and mineral oil mull spectra could be recorded and it is interesting to find that they are identical with one another. It has therefore been suggested that the absorption spectrum of any mineral can be studied by preparing its mineral oil mull in case it cannot be cut and polished into a thin crystal suitable for absorption work. The crystal field parameters derived for the two samples of Garnierite are identical and they are B = 845 cm^?1, C = 3.9 B, Dq = 422 cm^?1 and λ = ? 275 cm^?1.     

The D2Σ+ − X2Σ+ system of A10

Eleven bands of A10 belonging to the system (D² Σ ⁺-X² Σ ⁺) in the ultra-violet region have been analysed for their rotational structure. These are the 0-2, 1-3, 2-4, 0-3, 1-4, 3-0, 4-1, 3-1, 4-0, 5-1 and 6-1 bands lying at 2611.8Å, 2620.7Å, 2629.4Å, 2677.4Å, 2685.7Å, 2347.7Å, 2358.3Å, 2402.2Å, 2305.8Å, 2316.7Å and 2277.3Å respectively. The spin-splitting for the D² Σ ⁺ state has been determined from the doubling of the rotational lines observed for the bands 0-2, 1-3, 2-4 and 1-4. The rotational and vibrational constants (in cm^?1) evaluated for the D² Σ ⁺ state are: $$\begin{gathered} T_a = 40267 \cdot 6 \hfill \\ G(V) = 817 \cdot 47 (v + 1/2) - 4 \cdot 795 (v + 1/2)^2 - 0 \cdot 1107 (v + 1/2)^3 \hfill \\ B_v = 0 \cdot 56522 - 0 \cdot 0046 (v + 1/2) - 0 \cdot 00005 (v + 1/2)^2 \hfill \\ \gamma = 0 \cdot 004 \pm 0 \cdot 002 \hfill \\ \sigma = - 0 \cdot 4 \pm 0 \cdot 1 \times 10^{ - 6} \hfill \\ \end{gathered} $$      

Emission spectrum of chlorine excited in the presence of argon

The spectrum of chlorine excited in the presence of argon has been photographed with a 21-ft. grating spectrograph in the first order. Two band systems in the region 2600–2390 Å and 2365–2239 Å are observed which appear to be respectively analogous to the 2950–2670 Å and 2660–2590 Å systems of bromine reported earlier by Venkateswarlu and Verma. The wavelengths and the wavenumbers of all the bands in the system 2600–2390 Å are given. The vibrational scheme along with the corresponding Franck-Condon parabola is also given. The analysis suggests that the lower state of the system is the 3π(O _u ⁺_ state established by Elliott at 17658 cm.^?1 and that the upper state is at 67773 cm.^?1 The vibrational constants obtained arew ₀′ = 246·6 cm.^?1,w ₀′x ₀′ = 0·615 cm.^?1,w ₀″ = 255·2 cm.^?1,w ₀″x ₀″ = 5·5 cm.^?1,w ₀″y ₀″ = ?0·0155 cm.^?1 andw ₀″z ₀″ = 0·00115 cm.^?1     

Optical absorption of Co2+ doped NH4Cl: Phase transformation studies

The absorption spectrum of Co²⁺ doped NH₄Cl has been studied from the room temperature to the liquid nitrogen temperature. A sudden change in the spectrum is observed between 243° K and 233° K which is attributed to the phase transition in the crystal. From the observed spectrum it is suggested that Co²⁺ goes in interstitially as well as substitutionally. Both the types of centers exist at room temperature, but with decrease in temperature substitutional ions migrate to interstitial sites, the process being stimulated at the phase transformation point so that the 77° K spectrum seems to be mostly due to the interstitial centers. The 77° K spectrum is analyzed in the approximation of octahedral symmetry for interstitial ions and the band positions are fitted fairly well with B = 870 cm.^?1 Dq = 850 cm.^?1 and C = 4·4 B. A blue shift of about 100 cm.^?1 is observed for⁴T₁ (P) band at the phase transition which is attributed to the increase in Dq value with the anomalous lattice contraction at the phase transition. The decrease in the lattice parameter calculated from this blue shift is around 0·4% which is in good agreement with the results of X-ray measurements. Two possible models for the interstitial complex are examined and the one with fourfold chlorine coordination associated with two neutral water molecules at the first neighbour (NH₄)⁺ site lying along < 100> direction is suggested to be more probable.     

Emission spectrum of chlorine excited in the presence of argon

The weak band system in the region 2365-2239 Å is discussed in this paper. The wavelengths and the wavenumbers of the bands photographed with the first order of a 21-ft. grating spectrograph are recorded. The vibrational analysis of the bands and their corresponding intensity distribution are also given. The analysis shows that the lower state of the system is the same as that of the 2600-2390 Å system discussed in the earlier paper and is the 3π (O_u ⁺) state established by Elliott at 17658 cm.^?1 The constants of the upper state arew ₀′ = 261·5 cm.^?1,w ₀′x ₀′ = 0·812 cm.^?1, T₀=61290 cm.^?1.     

F2Δr−A2Πi band system of CN

The spectrum of CN has been studied in condensed electrical discharge through flowing CH₃CN vapour. Ten new bands of F²?,?A²Π_i system in the region 2100–2700 Å are obtained. The vibrational constantsω ₀′ = 1229.7 cm.^?1 and ω₀′χ₀′= 14.0 cm.^?1 are obtained for the first time for the²Δ state of CN.     

Isotope shift studies of the ultra-violet and visible bands of P16O and P18O

The spectra of P¹⁶O and P¹⁸O were excited in sealed discharge tubes containing neon (2–3 mm. pressure), oxygen gas enriched to 65 per cent. of¹⁸O and trace amounts of phosphorus vapour and photographed on a 3 m. grating spectrograph at a dispersion of 2·5 Å/mm. Isotope shift studies in theβ-bands confirmed the earlier vibrational scheme of Curryet al. and showed conclusively that the red as well as the violet degraded bands belonged to the sameβ-system. The present studies of isotope shifts also confirmed the vibrational assignments of the extensive ultraviolet bands involving the² Σ ^??X² Π transition and theγ-bands (A² Σ ⁺?X² Π). In the case of the visible bands, they provided evidence for the first time that the bands at 5585 Å, 5962 Å and 6385 Å belonged to one system and involved 0–0, 0–1 and 0–2 transitions respectively.     

Vibrational spectra and normal vibrations of acetanilide and N-deuterated acetanilide

The Raman and infra-red spectra of acetanilide and N-methylacetamide and of their N-deuterated compounds have been recorded. The vibrational frequencies of acetanilide have been assigned and the nature of the Amide I, II and III bands in acetanilide and N-methylacetamide has been investigated by the study of the changes in the frequencies of these bands in the spectra of their deuterated compounds. Acetanilide and deuterated acetanilide molecules have been subjected to normal co-ordinate treatment and the mixing up of the skeletal frequencies arising out of the in-plane vibrations has been determined. These results indicate that as in secondary amides, the amide II and amide III bands in acetanilide are due to the combined contribution ofδ (NH) andν (C-N) vibrations, but the contribution ofν (C-N) to the amide II band is less in acetanilide and deuterated acetanilide than in cases of N-methylacetamide and deuterated N-methylacetamide.     

Rigidity spectrum of cosmic ray helium nuclei

An experiment has been carried out using an oriented stack of nuclear emulsions to determine the rigidity spectrum of cosmic ray helium nuclei between 12 and 40 GV, by taking advantage of the variation of the geomagnetic cut-off rigidity in the east-west plane over Hyderabad, India. Altotal of 2433 identified helium nuclei recorded in the stack, has been divided into 8 angular intervals in the east-west plane corresponding to 8 different cut-off rigidities. From this the integral fluxes of helium nuclei at the top of the atmosphere have been obtained for all the 8 rigidity intervals. The vertical flux above an effective threshold rigidity of 16·73 GV has been determined with high statistical accuracy and has a value of 15·0±0·5 helium nuclei (m².sr.sec.)^?1. The rigidity spectrum of these nuclei between 12 and 40 GV can be well represented by a power law of the type N (>R) =1990 R^?1.74±0.11 (m².sr.sec.)^?1 and is the first direct determination so far made in this rigidity region. The differential rigidity spectra of protons, helium nuclei and S-nuclei of the cosmic radiation in the vicinity of the earth at solar minimum (1965) have been constructed with the existing world data and it is found that for rigidities ? 10 GV, the three spectra have, within experimental errors, the same slope of 2·6. The ratio P/He and He/S of the differential fluxes have been studied as a function of rigidity. It is found that for R>2 GV, the ratio P/He has, within experimental errors, a constant value of 6·3; as for the ratio He/S, it seems that the experimental data above a GV is not inconsistent with a constant value of 14 over the entire rigidity interval considered here.     

Spectral studies on some organic complexes of uranyl ion

The absorption spectra of new crystalline uranyl complexes with pyridine, at 80° Kare described. Pyridine uranyl chloride crystallises in two forms, both forms give sharp line like bands at low temperatures. In Form I the bands are analysed in terms of five electronic transitions F, M, D, U and SU of which the former four were suggested for uranyl ion by Diekeet al. Results on analogous compounds with deuteropyridine are also reported. Chloride complex seems to have pyridine in the first co-ordination sphere while the acetate complex is of the type of double salt.