  The dynamical evolution of terrestrial planets resembling Mercury in the
vicinity of spin-orbit resonances is investigated using comprehensive harmonic
expansions of the tidal torque taking into account the frequency-dependent
quality factors and Love numbers. The torque equations are integrated
numerically with a small step in time, includng the oscillating triaxial torque
components but neglecting the layered structure of the planet and assuming a
zero obliquity. We find that a Mercury-like planet with its current value of
orbital eccentricity (0.2056) is always captured in the 3:2 resonance. The
probability of capture in the higher 2:1 resonance is approximately 0.23. These
results are confirmed by a semi-analytical estimation of capture probabilities
as functions of eccentricity for both prograde and retrograde evolution of spin
rate. As follows from analysis of equilibrium torques, entrapment in the 3:2
resonance is inevitable at eccentricities between 0.2 and 0.41. Considering the
phase space parameters at the times of periastron, the range of spin rates and
phase angles, for which an immediate resonance passage is triggered, is very
narrow, and yet, a planet like Mercury rarely fails to align itself into this
state of unstable equilibrium before it traverses the 2:1 resonance.
