Medium Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Developmental
Confusion; Distraction; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Separated Traffic; Flight Crew Returned To Clearance
Procedure
Aircraft X was at FL350; landing LEX.  Aircraft Y was handed off to me from Sector 95 at FL360.  I descended Aircraft X to FL240.  When Aircraft X was observed leaving FL350; I descended Aircraft Y to FL350.  The 2 aircraft went into conflict alert about 10 seconds later.  Aircraft Y said he had an RA and was climbing. I called the traffic to Aircraft Y and within 15 seconds Aircraft Y said the RA was over and he was returning to FL350.The only recommendation I can think of is to make sure the aircraft are using the same rate of descent.  The aircraft involved were comparable in descent profiles but Aircraft X obviously was not maintaining normal rate of descent.  With that being said; the rule in Chapter 5 of the 7110.65 was applied correctly.
ZID Developmental uses the altitude leaving rule and ends up having a loss of separation.