Nuclear spin symmetry conservation

M. Quack The violation of the principle of nuclear spin symmetry conservation [1] could be seen in a similar scheme as I discussed for parity, but, in contrast to parity violation, it can also be seen by more standard spectroscopic techniques (and has been seen repeatedly). On the other hand, one might also look for violations of the Pauli principle, which in fact we have done [2]. However, it seems unlikely to find such a violation (and nothing of that kind has ever been found), although in principle one must allow even for such a phenomenon. 

The Principle of Approximate Parity and Nuclear Spin Symmetry Conservation and Other Approximate Symmetries of Adiabatic Channels... 

The quantum numbers tliat are appropriate to describe tire vibrational levels of a quasilinear complex such as Ar-HCl are tluis tire monomer vibrational quantum number v, an intennolecular stretching quantum number n and two quantum numbers j and K to describe tire hindered rotational motion. For more rigid complexes, it becomes appropriate to replace j and K witli nonnal-mode vibrational quantum numbers, tliough tliere is an awkw ard intennediate regime in which neitlier description is satisfactory see [3] for a discussion of tire transition between tire two cases. In addition, tliere is always a quantum number J for tire total angular momentum (excluding nuclear spin). The total parity (symmetry under space-fixed inversion of all coordinates) is also a conserved quantity tliat is spectroscopically important. 

More than forty years ago, Lee and Yang [8] observed anomalies in the decay patterns of theta and tau mesons, which suggested to them that parity was not conserved for certain weak interactions involved in the (3-decay of radioactive nuclei. This Nobel-prize-winning prediction was experimentally validated by Wu et al., [9] who found that the longitudinally polarized electrons emitted during the (3-decay of Co nuclei had a notable (40%) left-handed bias, i.e., their spins were predominantly antiparallel to their directions of motion. These experiments established that parity violation and symmetry breaking occurred at the nuclear level. 

Prior to excitation, the molecule is in the lowest vibrational state of the lowest electronic state (ground state), Sq. The absorption of a photon is governed by optical selection rules [2]. Its probability is proportional to the square of the transition dipole moment. The most severe restriction concerns the spin conservation. Further restrictions reflect the symmetry and overlap of corresponding wave functions. Regardless of the probability (reflected by the molar absorption coefficient), the single act of transition to a higher excited state due to absorption of a photon belongs to the fastest processes that occur in nature (except nuclear processes) and proceeds on timescales shorter than 10 s [3]. In this short time, neither the position of... 

Invariance with Respect to Inversion-Parity Invariance with Respect to Charge Conjugation Invariance with Respect to the Symmetry of the Nuclear Framework Conservation of Total Spin Indices of Spectroscopic States... 

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