OPERROR LOSS OF SEPARATION BTWN ACR X AND ACR Y ON CONVERGING OPPOSITE DIRECTION COURSE AT THE SAME ALT.

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I WAS THE CTLR WORKING AT FWA HIGH ALT RADAR SECTOR. TFC WAS HVY AND COMPLEX DUE TO WX IN OUTLYING SECTORS. I INITIALLY DSNDED ACR X TO FL280 TO START DSCNT INTO COLUMBUS. I ALSO HAD ACR Y ON FREQ AT FL280 ENRTE TO ORD ON A VECTOR. NEITHER MYSELF; NOR THE MANUAL CTLR (RADAR QUALIFIED) RECOGNIZED THE PROB AT THIS TIME. A FEW SECONDS LATER; I RECOGNIZED THE PROB AND BEGAN TO ISSUE CLRNCS TO EFFECT SEPARATION. THIS BEGAN WHILE THE ACFT WERE 12-14 MI SEPARATED THOUGH HEAD ON. I ISSUED ACR X A L TURN TO A 360 DEG HDG (HE WAS ON A 135 DEG HDG AT TIME; IN DSCNT TO FL280 OUT OF FL284). I IMMEDIATELY ISSUED A CLRNC TO ACR Y TO MAKE A L TURN TO HDG OF 180 DEGS; HOPING TO SAVE SIT BY PROVIDING LATERAL SEPARATION. ACR Y ACKNOWLEDGED TURN; ACR X DID NOT. I RECLRED ACR X TO EXPEDITE TO FL270 AND EVENTUALLY TO FL250 THINKING THAT AN ACFT ALREADY IN DSCNT CAN INCREASE RATE QUICKLY WHILE ACFT IN LEVEL FLT COULDN'T. NO RESPONSE FROM ACR X. AT THIS TIME I NOTICED ACR Y ALT READOUT NOW SHOWED FL275. MY FIRST INCLINATION WAS A MODE 'C' SWAP DUE TO OTHER ACFT IN VICINITY BUT I QUERIED ACR Y WITHOUT ADEQUATE RESPONSE. THE ACR Y ALSO HAD NOT STARTED TURN NOR HAD ACR X. I AGAIN RESTATED ALT CLRNC TO ACR X FIGURING ACR Y WAS INTO TURN AND LEVEL AT FL280; GOT A GARBLED RESPONSE. I THEN SAW ACR Y ALT READOUT SHOWING FL271 AND THEN ACR Y ALT NOW SHOWED FL274. I IMMEDIATELY ASKED FOR ALT ON ACR Y AGAIN AND RESTATED HE WAS SUPPOSED TO BE AT FL280. HE REPLIED HE WAS AT FL268 AND RESPONDING TO TCASII 'RA.' BY THIS TIME; THE ACFT WERE PAST EACH OTHER SAFELY. I DO NOT KNOW WHETHER ACR X ALSO RESPONDED TO TCASII 'RA' AND SHALLOWED OUT HIS DSCNT OR JUST NEVER GOT THE FIRST AND SECOND CLRNCS FOR AN EXPEDITED DSCNT OR TURN. THROUGHOUT THE WHOLE SEQUENCE; I BELIEVED ACR Y FLT WAS IN THE TURN AWAY FROM ACR X. THERE WAS 25 SECONDS FROM CLRNC TO LOSS OF 5 MI SEPARATION AND IF ACR Y HAD TURNED AND ACR X NOT TURNED; ACR X WOULD HAVE PASSED BEHIND. WHATEVER ELSE OCCURRED; MASSIVE CONFUSION WAS CAUSED WHEN NEITHER ACFT TURNED AND THEN ACR Y DSNDED WHILE I STILL THOUGHT ACR X WAS EXPEDITING TO A LOWER ALT. I HAVE BEEN DOING THIS FOR 25 YRS AND HAVE NEVER BEEN SO SCARED; CONFUSED AND MAD ALL AT THE SAME TIME. I LITERALLY HAD NO IDEA WHAT ELSE TO DO TO TRY AND SEPARATE THOSE ACFT. HOW TO PREVENT THIS PARTICULAR SCENARIO FROM RE-OCCURRING I'M NOT QUITE SURE. I'M HUMAN AND MISTAKES HAPPEN. IN THIS CASE; I THOUGHT I HAD CAUGHT THE MISTAKE IN TIME TO KEEP THE ACFT FROM BEING AS CLOSE AS THEY WERE BUT NOTHING I DID SEEMED TO TAKE ANY EFFECT. SUPPLEMENTAL INFO FROM ACN 314160: CTR TOLD US TO MAKE 'AN IMMEDIATE L TURN TO 180 DEGS; KEEP IT TIGHT.' AFTER 2-3 SECONDS INTO THE L TURN; WE GOT A TCASII RA; 'DSND; DSND!' CAPT TOOK ACFT; DEPLOYED SPDBRAKES; DUMPED THE NOSE AND BROUGHT PWR LEVERS TO IDLE; TO COMPLY WITH RA. THERE WAS A LOT OF CHATTER ON THE RADIO; AND I DO NOT REMEMBER ANYTHING THAT WAS SAID AFTER OUR 'TURN TO 180 DEGS;' THOUGH I DO REMEMBER THAT THE CTLR'S VOICE WAS 'PANICKY.' WE WERE ABOUT FL265 WHEN I SAW THE ACFT GO OVER THE TOP OF US. THE CTLR HAD VECTORED US INTO THE TFC; AND IF IT WASN'T FOR THE TCASII SYS; WE WOULD HAVE FLOWN HEAD-ON INTO THE OTHER ACFT AT A CLOSURE RATE OF OVER 1000 MPH! PAX AND FLT ATTENDANTS WERE STARTLED BUT UNINJURED. SUPPLEMENTAL INFO FROM ACN 313652: OUR TCASII ISSUED A TA; FOLLOWED IMMEDIATELY BY A 'DSND' RA COMMANDING APPROX A 2000 FPM DSCNT. I IMMEDIATELY BEGAN TO SEARCH FOR THE TFC INDICATED ON THE TCASII. I DO NOT RECALL WHAT ELSE WAS SAID BY ZAU; HOWEVER; I DO KNOW THE CTLR WAS TALKING TO SEVERAL ACFT. I BELIEVE HE CALLED US MORE THAN ONCE AND WE DID NOT ANSWER THE CALL DUE TO THE APCHING TFC. APPROX 15-20 SECONDS AFTER THE INITIAL TCASII RA; I SAW ANOTHER ACFT PASS OVERHEAD AND TO THE L OF OUR ACFT. I ALSO BELIEVE OUR L TURN; INSTRUCTED BY ATC; PROBABLY CAUSED US TO COME CLOSER TO THE OTHER ACFT. I BELIEVE WE TURNED L TO AT LEAST 200 DEGS BEFORE TURNING R AGAIN. WHEN INITIALLY SEEN ON OUR TCASII; THE OTHER ACFT WAS DIRECTLY OFF OUR NOSE; OPPOSITE DIRECTION; APPROX 600 FT ABOVE US; DSNDING. OUR ACFT WAS INITIALLY SLOW TO RESPOND TO THE TCASII ALERT (1-3 SECONDS DELAY). SUPPLEMENTAL INFO FROM ACN 313660: AT CRUISE; FL290; CTR TOLD US TO DSND TO FL240. APPROX 10 SECONDS LATER WHILE ON A 120 DEG HDG; CTR TOLD US TO TURN 360 DEGS AND GET TO FL240. HE TOLD ACR Y FLT TO TURN A HDG AND ALT. APPROX 5 SECONDS LATER OUR TCASII ALERTED US OF TFC. TCASII THEN WENT INTO A RA. IT GAVE US A MONITOR VERT SPD ALERT. CTR WAS STILL YELLING TO TURN TO 360 DEGS AND DSND TO FL240. WE COULD TELL HIS VOICE WAS QUITE FRAZZLED. TCASII RA CHANGED TO 'CLB; CLB.' WE STOPPED OUR TURN AND STARTED A SHALLOW CLB. WE LOOKED TO SEE THE B727 IN A R TURN APPROX 800 FT FROM US. WE BOTH ARE TOTALLY CONVINCED THAT BECAUSE OF TCASII WE AVOIDED GETTING CLOSER TO THE B727. WE FOLLOWED THE RA AS DISPLAYED AND EVERYTHING WORKED OUT GREAT.