DIFF USION OF POTA SSIUM ON T HE W(112) PLA NE PRE A DSORBE D BY Ni ATOM S: FI ELD EM ISSION CU RRE NT FLU CTU ATI ON S | AU TOCORRE LA TI ON STU DY

Di ̃usio n of potassium adsor bate on the W (112) plane w ith preadsorb ed nickel was investigated by means of the auto correlati on function of Ùeld emission current Ûuctuations. A comparison of the exp erimental auto correlation function with that of a theoretical calculati on by Gesley and Swanson gives the surf ace di ̃usi on coe£cient of potassium. From its temp erature dep endence the di ̃usio n activ ation energy at several N i precoverages for a constant potassium co verage ( È K = 0: 4) is derived. T he dep endence of the activ ation energy for potassium surf ace di ̃usi on on the nickel coverage | Ùrst reduction and then an increase with increasing N i coverage | is observed. T his is in agreement with the results obtained from the spectral analysi s of the Ùeld emission current Ûuctuation s of the same system. T he decrease is understo od to b e a result of the smoothing e ̃ect caused by N i atoms on the W(112) plane.