It is important to evaluate the total spin angular momentum of alkali-metal atoms if the atoms serve as a reservoir of angular momenta. We use an absorption-monitoring technique to measure $\ensuremath{\langle}{F}_{z}\ensuremath{\rangle}$, i.e., the expectation values of the quantization (
z) axis components of the total angular momentum of Cs atoms in the electronic ground state in both uncoated and antirelaxation-coated vacuum cells at room temperature. Cs atoms are polarized via optical pumping and probed using their
D2 transitions. The probe laser frequency is varied across the Doppler-broadened
D2 transition; the $\ensuremath{\langle}{F}_{z}\ensuremath{\rangle}$ values are derived using the integrated absorption coefficients. The largest $\ensuremath{\langle}{F}_{z}\ensuremath{\rangle}$ is 2.5 for the coated cell. We then use a simple model of spin flow through vapor cells to estimate the atomic spin relaxation probabilities after a single surface collision.
It is theoretically predicted that an isolated narrow resonance in the elastic scattering of electrons by alkali-metal atoms (M) gives rise to a single maximum in the n dependence of the total cross sections of high-Rydberg atoms A** in the highest allowed angular momentum states with M if the resonance width is roughly equal to or larger than the width of a single peak of the electron momentum distribution of the Rydberg states with highest angular momentum, i.e. l=n-1. This can be used to detect the narrow resonance theoretically predicted in e-M elastic scattering at ultra-low energies.
The conventional description of angular momentum in atomic physics divides the total angular momentum of an electron into an orbital part, L, and a spin part, S. In this work we propose the existence of an additional, hidden component of angular momentum, L_h, that is not directly observable through standard measurements of L or S but contributes to the full algebraic structure of the atomic system. We construct a formalism in which the total angular momentum operator J is expressed as J = L + S + L_h, and we show that L_h satisfies a set of commutation relations with the Hamiltonian that guarantee its conservation in isolated atoms. The hidden component is shown to arise naturally from the coupling of the electron's intrinsic spin to the electromagnetic field in a gauge-invariant manner. We discuss the theoretical implications of L_h for the spectrum of hydrogenic atoms and for multi-electron systems, and we propose that high-precision spectroscopic techniques, such as optical lattice clocks and quantum logic spectroscopy, can detect the influence of L_h through subtle shifts in energy levels and selection rules. The presence of hidden angular momentum suggests that the set of quantum numbers needed to fully characterize atomic states should be expanded, potentially leading to new insights into atomic structure and to the identification of previously unobserved spectral lines.