ZZZ controller described conflict event when traffic at FL430 experienced a pressurization emergency...

Narrative:

Aircraft X level at FL430 requested FL410. I descended the aircraft to FL410. The pilot declared an emergency and requested lower with the latter part of his transmission unreadable. I cleared aircraft X to FL380 ( the lower vertical limit of my airspace). I issued merging target procedures to aircraft X for traffic at 2 o'clock; eight miles; southbound; an airbus at FL370. The pilot did not reply. I issued traffic again to aircraft X and advised the airbus was descending through FL365 and a response came over the frequency 'blocked'. My radar associate walked over to the sector 30 and pointed to the data block of aircraft X; which had been forced onto the sector 30 and manually coordinated the emergency status of the aircraft and that it was in an emergency descent. Traffic was again issued to aircraft X for the airbus at FL360 descending and a frequency change to sector 30 was issued. I issued a traffic alert; 'traffic right underneath you; an airbus at FL350'. The pilot then checked on sector 30's frequency. The traffic for aircraft X was an A319. Air carrier Y received a TCAS alert and descended to avoid aircraft X.

Original NASA ASRS Text

Title: ZZZ Controller described conflict event when traffic at FL430 experienced a pressurization emergency; initiated a descent creating a TCAS RA with traffic below on another sector.

Narrative: Aircraft X level at FL430 requested FL410. I descended the aircraft to FL410. The pilot declared an emergency and requested lower with the latter part of his transmission unreadable. I cleared Aircraft X to FL380 ( the lower vertical limit of my airspace). I issued merging target procedures to Aircraft X for traffic at 2 o'clock; eight miles; southbound; an airbus at FL370. The pilot did not reply. I issued traffic again to Aircraft X and advised the airbus was descending through FL365 and a response came over the frequency 'Blocked'. My radar associate walked over to the Sector 30 and pointed to the data block of Aircraft X; which had been forced onto the Sector 30 and manually coordinated the emergency status of the aircraft and that it was in an emergency descent. Traffic was again issued to Aircraft X for the airbus at FL360 descending and a frequency change to Sector 30 was issued. I issued a traffic alert; 'Traffic right underneath you; an Airbus at FL350'. The pilot then checked on Sector 30's frequency. The traffic for Aircraft X was an A319. Air Carrier Y received a TCAS alert and descended to avoid Aircraft X.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	869820
Time
Date	201001
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Aircraft 1
Make Model Name	Citation X (C750)
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	None
Flight Plan	IFR
Aircraft 2
Make Model Name	A319
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Person 2
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

ZZZ controller described conflict event when traffic at FL430 experienced a pressurization emergency; initiated a descent creating a TCAS RA with traffic below on another sector.