ZDC center controller reported a loss of separation between two aircraft while working 6 sectors.

Attributes
ACN	1748275
Time
Date	202007
Local Time Of Day	1201-1800
Place
Locale Reference	ZDC.ARTCC
State Reference	US
Aircraft 1
Make Model Name	Medium Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Other Holding Pattern
Flight Plan	VFR
Aircraft 2
Make Model Name	Small Aircraft Low Wing 1 Eng Retractable Gear
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 16
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict

Narrative:

Aircraft X was doing VFR air work in the vicinity of mol VOR at FL145. He was maneuvering in the area of aircraft Y who was climbing out of FL140 to FL190 direct ldn. I attempted to reach aircraft X a few minutes prior to the event occurring with no response.when it became apparent that the traffic was [now] head on; I gave a 30L turn to aircraft Y. After giving that turn aircraft X reported he was responding to an RA and I saw him descend. Standard separation was quickly attained by the actions of aircraft X.workload and frequency congestion was a factor at the time. I was working 6 sectors. The sectors should have been split or a d-side would have been helpful.

Original NASA ASRS Text

Title: ZDC Center Controller reported a loss of separation between two aircraft while working 6 sectors.

Narrative: Aircraft X was doing VFR air work in the vicinity of MOL VOR at FL145. He was maneuvering in the area of Aircraft Y who was climbing out of FL140 to FL190 direct LDN. I attempted to reach Aircraft X a few minutes prior to the event occurring with no response.When it became apparent that the traffic was [now] head on; I gave a 30L turn to Aircraft Y. After giving that turn Aircraft X reported he was responding to an RA and I saw him descend. Standard separation was quickly attained by the actions of Aircraft X.Workload and frequency congestion was a factor at the time. I was working 6 sectors. The sectors should have been split or a D-side would have been helpful.

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.