Questions and Answers for Chapter 4


(1)       An elastic fluid is a fluid whose properties can be approximated as those of a harmonic oscillation and which possesses sufficient cohesiveness to maintain its structure and to transmit disturbances.


(2)       The +1, 0, -1 symbol refer to a limiting isotropic (spherical) system which has no directional properties and the spins line up precisely in an external magnetic field.  In this limit the spin angular momentum is a good quantum number so the state can be characterized as T-1, T0 T+1. .  This is an accurate representation of a radical pair or weakly coupled biradical.  It is not appropriate for a molecule, since molecules do not have cylindrical symmetry (exception: C60!)


For molecules when the system has roughly cylindrical symmetry for the orbitals involved in the triplet, the cylindrical axis is label z and the other two as x,y.  Group theory and MOs are used to decide how to label the axis in complex cases.  For the n,pi* state the z axis is the C-O bond assuming rough cylindrical symmetry.