  In this work, a one-dimensional direct implicit particle-in-cell/Monte Carlo
collision (PIC/MCC) code is used to study the capacitive discharge driven under
60 MHz rf power in the background gas of pure argon. The electron-induced
secondary electron emission (ESEE) model suitable for SiO$_2$ electrode is
taken into account. Several discharge modes are found in the transition region
between the higher-pressure glow discharge and the abnormal multipactor
discharge in this simulation. In a nerrow voltage range of hundreds of volts,
the abnormal multipactor will transform to normal multipactor with the
contining decrease of pressure. The characteristic of the three sustainale
discharges are given and anaysed, and their fomation porcess are discussed.
These new discharges have higher electron energy and electron flux at the
boundary and are mainly sustained by higher electrode-induced SEE coefficient
and high frequency. The appearence of the two multipactor modes in 60 MHz range
might broaden the theory of gas discharge and expand the application of
capacitive discharges.
