SQL & PL/SQL

Hello
Here's the model and the issue

SQL> create table t1 (id number, d date, vc varchar2(10));

Table created.

-- notice the special character in the index name 
SQL> create index t1_idx_mémo on t1(id); 

Index created.

Now I want to, say, rebuild this index (or any other action on this index)

SQL> select 
      'alter index '||owner||'.'||index_name ||' rebuild parallel 4;' 
            sql_stmt 
     from 
       all_indexes 
    where owner='C##MHOURI' 
     and table_name='T1';

SQL_STMT
---------------------------------------------------------------
alter index C##MHOURI.T1_IDX_M??MO rebuild parallel 4;

SQL> alter index C##MHOURI.T1_IDX_M??MO rebuild parallel 4;
alter index C##MHOURI.T1_IDX_M??MO rebuild parallel 4
               *
ERROR at line 1:
ORA-00911: invalid character

What would you do to fix this issue at the session level?
Thanks
Mohamed Houri