import re
regex = r"\bE\([A-Z]+\)(.*)"
test_str = "SCF Done: E(RHF) = -75.5859595965 A.U. after 10 cycles"
print(re.search(regex, test_str).group(1))
aW1wb3J0IHJlCnJlZ2V4ID0gciJcYkVcKFtBLVpdK1wpKC4qKSIKdGVzdF9zdHIgPSAiU0NGIERvbmU6IEUoUkhGKSA9IC03NS41ODU5NTk1OTY1IEEuVS4gYWZ0ZXIgMTAgY3ljbGVzIgpwcmludChyZS5zZWFyY2gocmVnZXgsIHRlc3Rfc3RyKS5ncm91cCgxKSkK