Excited states above the $$9^+$$
9
+
isomer in the odd-odd N = Z nucleus $$^{66}$$
66
As were studied by employing the $$^{40}$$
40
Ca($$^{28}$$
28
Si, pn) fusion-evaporation reaction at the Accelerator Laboratory of the University of Jyväskylä, Finland. A key method in this study was the use of conversion electrons emitted in the de-excitation of the isomeric state in $$^{66}$$
66
As as a tag for prompt $$\gamma $$
γ
rays. Several new states have been added to the $$^{66}$$
66
As level scheme, which was extended up to a tentative spin of 23$$\hbar $$
ħ
. The previously reported even-spin yrast band has been reassigned to have odd spin values. The odd-spin states above the $$9^+$$
9
+
isomer are compared with shell-model calculations using the jj44b and JUN45 interactions. Additionally, the recoil-$$\beta $$
β
tagging efficiency of the recently developed scintillator detector named Tuike has been determined experimentally for the first time.