Enhanced sensitivity to the time variation of the fine-structure constant and mp/me in diatomic molecules

Sensitivity to temporal variation of the fundamental constants may be strongly enhanced in transitions between narrow close levels of different nature. This enhancement may be realized in a large number of molecules due to cancellation between the ground state fine-structure omega(f) and vibrational interval omega(v) [omega = omega(f) - n omega(v) approximate to 0, delta omega/omega = K(2 delta alpha/alpha+0.5 delta mu/mu), K >> 1, mu = m(p)/m(e)]. The intervals between the levels are conveniently located in microwave frequency range and the level widths are very small. Required accuracy of the shift measurements is about 0.01-1 Hz. As examples, we consider molecules Cl-2(+), CuS, IrC, SiBr, and HfF+.