Articles written in Proceedings – Section A
Volume 1 Issue 7 January 1935 pp 419-424
Volume 2 Issue 1 July 1935 pp 63-66
The extended portion of rotation wings in liquids and the separate lines which take their place in the corresponding solids are explained as due to small oscillatory motions of molecules about their equilibrium positions. The motion is properly quantised in solids on account of the perfect crystalline arrangement and results in distinctly separated lines possessing definite frequency shifts. In liquids, there is only an imperfect quantisation on account of the quasi-crystalline arrangement and this results in a broadening of the lines into a continuous wing. A rough computation of the oscillation frequency in benzene from the specific heat data on the lines indicated by Pauling gives 72 cms.−1 which is of the expected order of magnitude. These oscillations, as pictured by Pauling, may be regarded as incomplete rotations and such a picture involves a direct relationship between the optical anisotropy of the molecule and the intensity of the scattered line. This is in accordance with the experimental fact that only substances like benzene and naphthalene which have a marked degree of anisotropy give rise to extended wings in the liquid state and lines in the solid state.
In conclusion the author desires to express his grateful thanks to Professor Sir C. V. Raman for his kind interest in the work.
Volume 2 Issue 1 July 1935 pp 86-91
The principal Raman lines in benzene, cyclopropane and ethane shifted by 992, 1188 and 993 wave numbers respectively are found to have feeble companion lines of frequency shifts 985, 1175 and 974. These are attributed to molecules in which one of the carbon atoms is replaced by its heavier isotope C13,
In conclusion, the author desires to express his grateful thanks to Prof. Sir C. V. Raman for his kind interest in the work.
Volume 2 Issue 1 July 1935 pp 92-100
Volume 2 Issue 3 September 1935 pp 303-309
Volume 2 Issue 3 September 1935 pp 310-312
Volume 2 Issue 4 October 1935 pp 342-344
A study of the intensity distribution in the rotation wing accompanying the Rayleigh lines in liquid benzene in makde using a high dispersion spectrograph. The results are in perfect agreement with those obtained on earlier occasions using instruments of lower dispersion.
Volume 2 Issue 5 November 1935 pp 477-482
Measurements have been made of the intensity and polarisation of the lines in the Raman spectrum of deuterium. The results, when compared with those calculated from the theory of rotational Raman scattering due to Manneback, show satisfactory agreement.
The vibration Raman line in deuterium is found to exhibit a depolarisation factor of 0·18 and an intensity of about one-tenth the aggregate intensity of the rotational scattering. From-this result it is estimated that the intensity of the vibration line is about 1/300 of that of the Rayleigh line. This is an unusually large ratio for gases and has hitherto been found only in hydrogen.
Further work in relation to the fine structure of the vibration line and the inter-comparison of the P, Q and R branches is in progress and will form the subject-matter of the next paper in this series.
Volume 3 Issue 1 January 1936 pp 135-139
Two new bands at Δ
Volume 3 Issue 2 February 1936 pp 135-139
Two new bands at Δ
Volume 5 Issue 1 January 1937 pp 18-22
The Raman spectra of benzene in the liquid and vapour states have been photographed alongside each other under identical conditions of slit width and illumination. While the 600 and 992 Raman lines show no shift, the line at 3061 shifts to 3069 as we pass from the liquid to the vapour. The Raman line at 3047 observed in the liquid has either completely disappeared or considerably weakened in the vapour. The rotation wings accompanying the Rayleigh lines in the liquid show no intensity maximum separated from the centre whereas there is a distinct maximum in the case of the vapour. This result is demonstrated with the help of microphotometric records. The distribution of intensity within the wings in the case of the liquid is very different from that obtained in the case of the vapour. When judged by comparing with the 992 Raman line, a very considerable fall in the absolute intensity of the wings is noticed as we pass from the vapour to the liquid. The significante of this result is discussed.
Volume 7 Issue 1 January 1938 pp 35-37
Volume 7 Issue 3 March 1938 pp 245-250
Volume 8 Issue 2 August 1938 pp 101-114
Volume 8 Issue 2 August 1938 pp 115-118
Volume 8 Issue 2 August 1938 pp 119-123
Volume 8 Issue 5 November 1938 pp 345-348
Volume 9 Issue 3 March 1939 pp 224-258
Volume 9 Issue 4 April 1939 pp 312-315
Volume 10 Issue 4 October 1939 pp 224-228
Volume 11 Issue 1 January 1940 pp 62-71
Volume 12 Issue 3 September 1940 pp 337-339
Modified X-ray reflections, due to Cu Kα and Cu Kβ radiations from the (211) planes of calcite, have been recorded. Their positions are measired and the results lead to a spacing which remains nearly constant for all the settings studied. This agrees well with the standard value, namely 3 029 A.U.
Volume 13 Issue 4 April 1941 pp 266-268
Volume 13 Issue 6 June 1941 pp 543-563
Volume 16 Issue 6 December 1942 pp 359-365
Volume 16 Issue 6 December 1942 pp 366-368
Volume 18 Issue 5 November 1943 pp 251-256
Group theoretical methods have been applied for obtaining the normal oscillations of the diamond structure on the basis of a 16 atom cell as the repeating unit. It is shown that besides the translation, there are eight normal oscillations one of which is threefold degenerate, two of which are fourfold degenerate, three of which are sixfold degenerate and two of which are eightfold degenerate. Expressions are derived for the corresponding normal frequencies by postulating suitable potential energy functions.
Volume 19 Issue 2 February 1944 pp 108-110
Volume 20 Issue 3 September 1944 pp 122-127
Volume 20 Issue 5 May 1945 pp 298-303
Volume 20 Issue 5 May 1945 pp 304-309
Volume 21 Issue 1 January 1945 pp 19-23
Volume 23 Issue 5 May 1946 pp 254-256
Volume 26 Issue 2 August 1947 pp 97-109
Volume 28 Issue 2 August 1948 pp 54-62
Volume 32 Issue 3 September 1950 pp 197-199
It has been experimentally shown, by applying the ultrasonic wedge method, that the sound velocity in brass and aluminium plates is independent of frequency in the range 1 to 10 megacycles. For obtaining this result unambiguously, one has to use plates of proper thicknesses and lateral dimensions and eliminate coupling and boundary effects.
Volume 35 Issue 3 March 1952 pp 129-135
The ultrasonic wedge method has been used for a determination of the average values (C11′)AV and (C44′)AV in the case of certain polycrystalline aggregates of cubic compounds prepared by compressing finely divided powder under high pressures. The measured values are compared with the values calculated from the known single crystal constants. It is found that certain substances can be compressed till their densities closely reach the single crystal densities and in those substances the average elastic properties also closely reach the corresponding ideal values. In other cases, the compressibility of a pressed specimen depends to a marked degree upon its density.
Volume 37 Issue 3 March 1953 pp 350-376
Volume 37 Issue 5 May 1953 pp 585-588
Volume 37 Issue 5 May 1953 pp 589-591
Volume 41 Issue 3 March 1955 pp 72-90 Symposium on the Elasticity of Crystal
Volume 43 Issue 4 April 1956 pp 203-209
Volume 46 Issue 6 December 1957 pp 399-405
The paper furnishes measurements on the birefringence produced at different temperatures in crystals of NaCl, KCl and KBr when subjected to stress. The results show that the stress-optical coefficients (
Volume 52 Issue 1 July 1960 pp 1-19
In order to study the elastic behaviour of matter when subjected to very large pressures, such as occur for example in the interior of the earth, and to provide an explanation for phenomena like earthquakes, it is essential to be able to calculate the values of the elastic constants of a substance under a state of large initial stress in terms of the elastic constants of a natural or stress-free state. An attempt has been made in this paper to derive expressions for these quantities for a substance of cubic symmetry on the basis of non-linear theory of elasticity and including up to cubic powers of the strain components in the strain energy function. A simple method of deriving them directly from the energy function itself has been indicated for any general case and the same has been applied to the case of hydrostatic compression. The notion of an effective elastic energy—the energy require to effect an infinitesimal deformation over a state of finite strain—has been introduced, the coefficients in this expression being the effective elastic constants. A separation of this effective energy function into normal co-ordinates has been given for the particular case of cubic symmetry and it has been pointed out, that when any of such coefficients in this normal form becomes negative, elastic instability will set in, with associated release of energy.
Volume 58 Issue 1 July 1963 pp 1-5
A new and elegant method, based on group theory, has been given for obtaining the maximum number of force constants needed in expressing the potential energy of a vibrating molecule characterised by a certain point group symmetry.
Volume 58 Issue 4 October 1963 pp 183-196
Group theoretical methods are developed for studying two types of point defects in crystals, namely trapped and untrapped ones, and the relaxation phenomena that arise therefrom. It is pointed out that a very close analogy exists between the relaxation modes on the one hand and normal oscillations on the other. This analogy enables us to utilise many of the concepts developed and the results obtained earlier in connection with studies on molecular spectra and Raman effect for an investigation of the relaxation phenomena. Simple rules are given for writing out the modes, ascertaining their activity or otherwise in regard to external electric and mechanical fields, evaluating the relaxation times and so on. Specific examples which are of practical interest are worked out under both the classes of defects studied. The methods developed can be applied to any general case.
Volume 59 Issue 1 January 1964 pp 1-13
Application of group theoretical methods to a study of the effect of symmetry on the physical properties of the 32 crystal classes as given earlier by Bhagavantam has been extended in this paper to a similar study of the magnetic properties of the 90 magnetic crystal classes. Results obtained in various cases agree with those derived earlier by more elaborate methods.
Volume 60 Issue 1 July 1964 pp 1-10
A group theoretical method given by one of us in earlier publications for studying the effect of crystal symmetry on physical properties is now extended to cover the galvanomagnetic, thermomagnetic and piezo-galvanomagnetic effects in single crystals. These effects have gained importance in semi-conductor physics and such studies are therefore of current interest and may be expected to yield valuable new information.
Volume 63 Issue 6 June 1966 pp 391-399
One-dimensional, two-dimensional and three-dimensional magnetic lattices have been derived making use of methods adopted by the authors in an earlier paper in deriving cystallographic magnetic point groups.
Volume 66 Issue 1 July 1967 pp 33-39
Neumann’s principle is examined in the context of the recent generalizations relating to symmetry and physical properties of crystals. It is shown that the difficulties encountered in applying the principle to transport properties are only apparent and that it is not necessary to impose restrictions on the principle. A proper interpretation of the symmetry of crystals resolves the difficulties and brings out clearly the axiomatic nature of this principle and its universal applicability.
Volume 69 Issue 4 April 1969 pp 182-188
The phenomenon of piezoelectric relaxation in crystals has been dealt with briefly by applying group theoretical methods. Three typical crystal classes which are capable of exhibiting piezoelectricity are considered in some detail and a study is presented of the possible piezoelectric relaxation when different defect complexes are introduced in the crystals. The concept of an anisotropy in piezoelectric relaxation has been brought out in a crystal class belonging to the orthorhombic system.
Volume 73 Issue 6 June 1971 pp 269-274
From symmetry considerations and using generalized Onsager relations, it is shown that 66 of the 90 magnetic classes, consisting of 29 single colour and 37 double colour ones, can exhibit what may be called the strain gyrotropic rotation. Similarly, 69 of the 90 magnetic classes, consisting of 21 single colour and 48 double colour ones, can exhibit what may be called the strain gyrotropic birefringence. A crystal in the class m3 or m3
Volume 75 Issue 1 January 1972 pp 1-7
In an introductory section, the symmetry properties of some of the higher rank polar tensors relating to nonlinear optical polarization are briefly enumerated. It is noted that linear magneto-electric polarizability has been experimentally measured and that the reported results are in conformity with the theory. Symmetry properties of the higher rank axial tensors relating to nonlinear magneto-electric effect are enumerated and it is suggested that such an effect is possible in some crystals in the anti-ferromagnetic state. In all these studies, methods developed earlier by the author have been used.
Volume 76 Issue 1 July 1972 pp 13-20
A simple procedure, based on the transformation properties of the nonlinear susceptibility tensors of different ranks referred to appropriate coordinate systems, is given for studying the selection rules and polarization characters in regard to all orders of harmonics. By this procedure, results covering both linearly and circularly polarized incident light for all the 32 crystal classes with some simplifying restrictions are obtained and listed in the paper. Attention is drawn to special features in each case. There is complete agreement with what has been reported earlier by Tang and Herbert Rabin for circularly polarized incident light.