ZLC controller reported incorrectly sequencing aircraft resulted in an operational error.

Attributes
ACN	1682423
Time
Date	201909
Local Time Of Day	1201-1800
Place
Locale Reference	ZLC.ARTCC
State Reference	UT
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 8
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy

Narrative:

Aircraft X was on route level FL350. Aircraft Y was on a vector to achieve spacing landing slc at FL350. Aircraft X was a bit faster (I think 15 kts or so). I turned aircraft Y back to effta. My D side brought color on edst. This is when I realized the two aircraft were traffic. I descended aircraft Y to FL340 and turned aircraft X 30 degrees left. I told aircraft Y to report level FL340 and didn't get a read back. I was watching the ca (captain) on the scope and saw as close as 4.99 NM. First I should have scanned and noticed the traffic before turning aircraft Y back. Next I should have pushed aircraft Y down to FL330 (even though I don't think this would have saved it).

Original NASA ASRS Text

Title: ZLC Controller reported incorrectly sequencing aircraft resulted in an operational error.

Narrative: Aircraft X was on route level FL350. Aircraft Y was on a vector to achieve spacing landing SLC at FL350. Aircraft X was a bit faster (I think 15 kts or so). I turned Aircraft Y back to EFFTA. My D side brought color on EDST. This is when I realized the two aircraft were traffic. I descended Aircraft Y to FL340 and turned Aircraft X 30 degrees left. I told Aircraft Y to report level FL340 and didn't get a read back. I was watching the CA (Captain) on the scope and saw as close as 4.99 NM. First I should have scanned and noticed the traffic before turning Aircraft Y back. Next I should have pushed Aircraft Y down to FL330 (even though I don't think this would have saved it).

Data retrieved from NASA's ASRS site 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.