Nuclear Magnetic Resonance ANIMATED ILLUSTRATIONS MS Powerpoint Presentation Files Uses Animation Schemes as available in MS XP or MS 2003 versions A class room educational material File-11 Basic definitions for better appreciation of NMR http://ugc-inno-nehu.com/links_from_web.html 2/23/2019 11:31:15 AM S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM

After this illustration on magnetic Field, in the next slide, Magnetic Moments would be considered Presence of a Magnetic field is pictorially depicted by a vector-line pointing along the direction in which an isolated North pole would move S S Set of equally spaced parallel lines indicates homogeneous field No. of lines within a unit area of cross section [in plane perpendicular] Is the field strength/ Intensity of magnetic field It is important to realize the difference between two poles forming magnet pole faces and two poles making up the dipole with a dipole moment N N N Area of cross section Inhomogeneous Fields 2/23/2019 11:31:15 AM S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM

S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM While considering a magnet,it is the field in the space between the North pole face and South pole face which is pertinent. There is not much concern about using the field values at distant points from the poles! No dipole is assigned nor any moment is recognizable for the north & south poles. S When a dipole is considered, its moment is placed in the region between the two poles forming the dipole. And the field at distant points from the dipole is what is pertinent. ‘m’ is the pole strength, and ‘2l’ is the distance between the two poles Then the magnetic moment vector of magnitude μ is defined by: m S X The moment has the direction from south to the north. Thus this sense of the vector seems to be opposite to what was said of direction of field ! X N X X N 2l X X X The next slide describes the flowing currents causing magnetic moments and fields Primary moment at centre And Secondary field at points around the moment. And, the direction of movement of isolated north pole N m S An illustration of current flowing in a circular coil, direction of induced field at the centre and the secondary field distribution around and the movement of isolated north pole + N N N N 2/23/2019 11:31:15 AM S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM

S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM Such electron (charge cloud) circulations are inherently occurring in molecules and atoms, and not necessarily because of any applied external strong magnetic fields. If there is a current loop as shown in the left side, then the same can be considered equivalently as current flowing in the same specified sense in two adjacent circular paths Equivalent to +Charge flowing in the opposite direction Unsymmetrical paths/loops; a consideration ELECTRON FLOW Direction of Current Direction of flow of +ve charge Several of such circulations in a variety of paths can be simultaneously occurring (as would appear here in). Right hand rule is applied to determine the direction of the induced magnetic field 2/23/2019 11:31:15 AM S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM

S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM In the absence of external magnetic field The totality of the circulations could be as on the Left in effect + + + + + + + + + Further considerations begin with this description below + When an external magnetic field is applied + The extent to which the charge cloud get influenced by the a presence of an external field, and hence get altered in their charge cloud charactristics is called the Magnetic Susceptibility and is represented by the Greek letter (symbol) The magnetic susceptibility caused changes are said to induce a magnetic moment in the system which is given the symbol + + + + + 2/23/2019 11:31:15 AM S.A.- Chem. Seminar on Monday June 25, 2007 at 3:00PM