scholarly journals The scattering of neutrons by protons

1935 ◽  
Vol 149 (866) ◽  
pp. 176-183 ◽  
Keyword(s):  
Short Range ◽  
Wave Length ◽  
Interaction Force ◽  
Isotropic Scattering ◽  
Fast Neutrons ◽  
Exchange Force ◽  
Centre Of Gravity ◽  
Ordinary Type ◽  
The Asymmetry ◽  
Limits Of Error

1. The mass defects of the lightest nuclei, particularly the ratio between that of the diplon and the α -particle, make it very probable that the range of the interaction force between proton and neutron is very small, of the order of about 10- 13 cm. Therefore, in all experiments in which scattering of neutrons by protons has been observed, their wave-length is larger than the range of the interaction force. In these circumstances it is well known that the scattering intensity will be independent of angle for that co-ordinate system in which the centre of gravity is at rest. For much higher energies, of course, this will no longer be true and one will expect then an anisotropy in the scattered intensity. This effect will become appreciable for energies for which the wave-length is of the same order as the range of the forces. Exact measurements of the angular distribution of scattered fast neutrons would therefore afford a direct check of the assumption of a short range and an estimate of this range. The existing experiments show an isotropic scattering within the limits of error, but are not accurate enough to allow very definite conclusions. 2. The importance of such experiments is further increased by the fact that, as was pointed out by Wick, the sign of the asymmetry in the scattering depends on whether the interaction is of the ordinary type or an exchange force as proposed by Heisenberg and Majorana, and observations of the asymmetry could therefore decide this question.

Conclusion

2017 ◽  
Author(s):  
Frédéric Grare
Keyword(s):  
United States ◽  
The United States ◽  
The Political ◽  
Slow Pace ◽  
Centre Of Gravity ◽  
The Us ◽  
The Future ◽  
Economic Interaction ◽  
The Asymmetry ◽  
The Relationship

India’s relationship with the United States remains crucial to its own objectives, but is also ambiguous. The asymmetry of power between the two countries is such that the relationship, if potentially useful, is not necessary for the United States while potentially risky for India. Moreover, the shift of the political centre of gravity of Asia — resulting from the growing rivalry between China and the US — is eroding the foundations of India’s policy in Asia, while prospects for greater economic interaction is limited by India’s slow pace of reforms. The future of India-US relations lies in their capacity to evolve a new quid pro quo in which the US will formulate its expectations in more realistic terms while India would assume a larger share of the burden of Asia’ security.

scholarly journals Consistent Treatment of Pion Exchange Force and Meson versus Quark Dynamics in the Nucleon?Nucleon Interaction

1993 ◽  
Vol 46 (6) ◽  
pp. 737
Author(s):  
GQ Liu ◽  
AW Thomas
Keyword(s):  
Vector Meson ◽  
Short Range ◽  
Coupling Model ◽  
Nucleon Nucleon ◽  
Pion Exchange ◽  
Meson Exchange ◽  
Exchange Potential ◽  
Exchange Force ◽  
Gluon Exchange ◽  
Vector Meson Exchange

To distinguish explicit quark effects from meson exchange in the NN interaction, it is necessary to splice the long-range meson exchange forces and short-distance dynamics due to quarks. However, in most quark model studies the short-range part of the pion exchange is usually treated differently, which makes it difficult to get a uniform picture of the short-range dynamics. We make a comparison between meson exchange and quark-gluon dynamics using the same pion exchange potential based on a quark-pion coupling model. The roles of vector meson exchange and gluon exchange in the NN interaction are compared by calculating NN phase parameters. It is shown that, with this consistent one-pion exchange force, the vector meson exchange gives a better fit to the data. This suggests that non-perturbative mechanisms responsible for meson exchange may need more careful handling to supplement the usual one-gluon exchange mechanism in describing the NN interaction.

scholarly journals Accurate, explicit formulae for higher harmonic force spectroscopy by frequency modulation-AFM

2015 ◽  
Vol 6 ◽  
pp. 149-156 ◽  
Author(s):  
Kfir Kuchuk ◽  
Uri Sivan
Keyword(s):  
Frequency Modulation ◽  
Short Range ◽  
Oscillation Amplitude ◽  
Complete Information ◽  
Interaction Force ◽  
Harmonic Force ◽  
Interaction Range ◽  
Present Letter ◽  
Explicit Formulae ◽  
Higher Harmonic

The nonlinear interaction between an AFM tip and a sample gives rise to oscillations of the cantilever at integral multiples (harmonics) of the fundamental resonance frequency. The higher order harmonics have long been recognized to hold invaluable information on short range interactions but their utilization has thus far been relatively limited due to theoretical and experimental complexities. In particular, existing approximations of the interaction force in terms of higher harmonic amplitudes generally require simultaneous measurements of multiple harmonics to achieve satisfactory accuracy. In the present letter we address the mathematical challenge and derive accurate, explicit formulae for both conservative and dissipative forces in terms of an arbitrary single harmonic. Additionally, we show that in frequency modulation-AFM (FM-AFM) each harmonic carries complete information on the force, obviating the need for multi-harmonic analysis. Finally, we show that higher harmonics may indeed be used to reconstruct short range forces more accurately than the fundamental harmonic when the oscillation amplitude is small compared with the interaction range.

Observation of Dislocation DisAppearance in Aluminum Thin Films and Consequences for Thin Film Properties

1997 ◽  
Vol 505 ◽  
Author(s):  
P. Müllner ◽  
E. Arzt
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Short Range ◽  
Dislocation Core ◽  
Interaction Force ◽  
High Temperature Strength ◽  
Film Properties ◽  
Aluminum Films ◽  
Transmission Electron ◽  
Diffusive Movement

ABSTRACTDislocation structures in Al-Cu thin films have been studied by transmission electron microscopy (TEM). We have observed that the contrast of interface dislocations disappears in the electron beam. We assume that the contrast dissolution is due to the spreading of the dislocation core at the crystalline/amorphous interface or due to a diffusive movement of the dislocation through the oxide. In any case, the relaxation is assumed to be controled by irradiation induced diffusion. As a consequence, the short range stresses and at least partly also the long range stresses of the dislocations relax. This relaxation changes the interaction force between dislocations and may thus significantly affect the mechanical properties of thin films. It is concluded that interaction between interface dislocations may not be responsible for the high temperature strength of aluminum films.

scholarly journals Concentration Fluctuation in Long Wavelength Limit in Liquid Magnesium Alloy

2011 ◽  
Vol 2 ◽  
pp. 47-49
Author(s):  
D Adhikari ◽  
B. P. Singh ◽  
I. S. Jha
Keyword(s):  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Wave Length ◽  
Concentration Fluctuation ◽  
Chemical Order ◽  
Long Wavelength ◽  
Long Wave ◽  
Associated Solution Model ◽  
Associated Solution

The microscopic structure of MgSn liquid alloy at 1073K has been studied by using regular associated solution model. For this we have calculated the concentration fluctuation in long wave length limit [SCC(0)] and chemical short range order parameter (α1) of liquid MgSn alloy at 1073 K.Keywords: Binary Alloy; Complex; Chemical order; Microscopic FunctionThe Himalayan Physics Vol.2, No.2, May, 2011Page: 47-49Uploaded Date: 1 August, 2011

scholarly journals The spectrum of magnesium hydride

1910 ◽  
Vol 83 (561) ◽  
pp. 210-210 ◽  
Keyword(s):  
Wave Length ◽  
Solar Spectrum ◽  
Magnesium Hydride ◽  
High Dispersion ◽  
Calcium Hydride ◽  
The Sun ◽  
Or Groups ◽  
Concave Grating ◽  
Limits Of Error ◽  
Reduced Temperature

The author has previously discovered that many of the band lines peculiar to the sun-spot spectrum are identical with lines composing the green fluting attributed to magnesium hydride by Liveing and Dewar. The present paper gives the results of a further investigation of this spectrum with high dispersion, together with details of wave-length determinations. The principal results may be briefly summarised as follows: -(1) No sufficient reason has been found for modifying Leveing and Dewar’s conclusion that the spectrum is produced by the combination of magnesium with hydrogen. (2) Lines are shown at short intervals in all parts of the spectrum from the extreme red to λ 2300, and definite groups of flutings begin at 5621.57, 5211.11, 4844.92, 4371.2, and near 2430. (3) From photographs of the magnesium arc in hydrogen at low temperatures, taken with a 10-foot concave grating, the positions of close upon 2000 lines composing the three principal bands have been determined. The wave-lengths were derived from the interference standards of Fabry and Buisson, but have been corrected to Rowland’s scale to facilitate comparsion with solar spectra. (4) Twelve of the series of none of the formulæ which have been proposed are sufficiently general in their application to represent all of these series within the limits of error of measurements. For the longer series the closest approximation is given by Halm’s equation. (5) The identification of magnesium hydride in the sun-spot spectrum has been fully confirmed, and is clearly demonstrated by photographs submitted for reproduction. (6) It is shown that many of the bright lines, but merely clear interspaces between lines or groups of lines in the spectrum of magnesium hydride. (7) The presence of the magnesium hydride flutings, together with flutings of titanium oxide and calcium hydride discovered at Mount Wilson, accords with the view that spots are regions of reduced temperature, and that their darkness is at least partly due to absorption. (8) The investigation of the possible presence of lines of magnesium hydride in the ordinary solar spectrum is for several reasons inconclusive, but there is evidence that very few, if any, of the thousands of faint lines tabluated by Rowland are to be accounted for by this substance.

scholarly journals Anomaly in energetic and structural properties of MgSn liquid alloys

BIBECHANA ◽  
1970 ◽  
Vol 7 ◽  
pp. 33-38
Author(s):  
A Kumar ◽  
IS Jha ◽  
BP Singh
Keyword(s):  
Lattice Model ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Wave Length ◽  
Range Order ◽  
Heat Of Mixing ◽  
Range Order Parameter ◽  
Molten State ◽  
Short Range Order Parameter

The observed asymmetry in the properties of mixing of MgSn alloy in molten state is successfully explained on basis of the quasi-lattice model. It has been utilized to determine the free energy of mixing, entropy of mixing, heat of mixing, the concentration- concentration structure factor in long wave-length limit [Scc(0)] and the Warren Cowley short range order parameter (α1) of MgSn alloy in molten state at 1073 K. The analysis suggests that heterocordiantion leading to the formation of chemical complex Mg2Sn is likely to exist in the melt but is of a weakly interacting in nature. The interaction energies between the species of the melt are found to depend considerably on temperature and the alloy is more ordered towards Mg rich region Keywords: Quasi-lattice model; Binary alloys; Short range order parameter; Asymmetry DOI: 10.3126/bibechana.v7i0.4042BIBECHANA 7 (2011) 33-38

Studies in jj -coupling. III. Nuclear energy levels

1952 ◽  
Vol 215 (1120) ◽  
pp. 120-132 ◽  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Short Range ◽  
Nuclear Energy ◽  
Energy Levels ◽  
Wave Functions ◽  
Light Nuclei ◽  
Radial Dependence ◽  
Exchange Force ◽  
Very High

The wave functions for the configurations j n , with j = 3/2, 5/2 and 7/2, obtained in part II of this series according to the particular scheme of part I, are here used to obtain the central force energy matrices for nuclear configurations. The ordering of energy levels is studied as a function of the nature of the force with especial reference to its range, and the results are presented in the form of energy-level diagrams. The ordering of levels predicted to hold in parts I and II when forces are of short range is shown to occur with practical ranges; but for light nuclei in particular it is demonstrated that levels of very high angular momentum may sometimes occur near to the ground state. The results are found to be largely independent of the precise nature of the forces provided they are of reasonably short range and are attractive in the 1 S state of two like particles; for definiteness, however, the diagrams have been drawn for a Rosenfeld symmetrical exchange force of Gaussian radial dependence. The effect of using other types of central interaction is discussed qualitatively. The lowest excited states of even-even nuclei are seen to have a simple interpretation in jj -coupling.

scholarly journals Sensitive micro-balances and a new method of weighing minute quantities

1909 ◽  
Vol 82 (558) ◽  
pp. 580-594 ◽  
Keyword(s):  
Maximum Load ◽  
New Method ◽  
Considerable Difficulty ◽  
Centre Of Gravity ◽  
Quartz Fibre ◽  
Ordinary Type ◽  
Micro Balance

In the course of experiments undertaken by the authors with a view to establishing a possible relation between the amount of ionisation produced at the surface of certain heated metals and the amount of oxidation of the metal, it became necessary to be able to measure changes of weight of the order of one-thousandth of a milligramme (1 X 10 -6 gramme). A micro-balance of the Nernst type was accordingly constructed which possessed the requisite sensitiveness, but considerable difficulty was experienced in obtaining consistent readings with it, owing chiefly to the inconstancy of zero and the great variation of sensibility with load. This latter defect is an inevitable consequence of the fact that a restoring couple due to gravity, the magnitude of which varies, as in the ordinary balance, with the position of the centre of gravity of the system relative to its point of suspension, is superposed on the restoring torque of the quartz fibre. Attempts to minimise this trouble led finally to the conclusion that for the purpose in view better results were to be expected from a gravity balance of the ordinary type in which the required degree of sensitiveness should be attained by making the beam very light. As the maximum load which it was intended to use on the balance was less than half a gramme, this could be done without loss of proportionate rigidity.

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