  We have studied the peculiarities of selective reflection from Rb vapor cell
with thickness $L <$ 70 nm, which is over an order of magnitude smaller than
the resonant wavelength for Rb atomic D$_1$ line $\lambda$ = 795 nm. A huge
($\approx$ 240 MHz) red shift and spectral broadening of reflection signal is
recorded for $L =$ 40 nm caused by the atom-surface interaction. Also
completely frequency resolved hyperfine Paschen-Back splitting of atomic
transitions to four components for $^{87}$Rb and six components for $^{85}$Rb
is recorded in strong magnetic field ($B >$ 2 kG).
