  We consider singular self-adjoint extensions for one-dimensional
Schr\"{o}dinger operator for two-component wave function within the framework
of the distribution theory for discontinuous test functions
\cite{funcan_deltadistr_kurasov_jmathan1996}. We show that among
$\mathds{C}^{4}$-parameter set of boundary conditions with state mixing there
is only $\mathds{R}^2$-parameter subset compatible with the spin interpretation
of the two-component structure of the wave function. For the spin
interpretation of such wave function they can be identified as the point-like
spin-momentum (Rashba) interactions. We suggest their physical realizations
based on the regularized form of the Hamiltonian which couples the electrical
field inhomogeneity to spin.
