Table 1.

Summary of major uncertainties associated with the absolute determination of the center frequency of the C₂H₂(ν₁ + ν₃) R(1)e ro-vibrational transition, for P_SCAR = 40 μW and f_Ac = f_He = 3 SCCM

Contribution	Uncertainty (kHz)
Statistical	1.1
Foreign collisional shift	0.01
Self collisional shift	0.01
Power shift	0.2
GPS-based reference chain	0.5
Second-order Doppler shift	0.02
Lamb-dip profile fit	0.07
Total	1.2 (6 ⋅ 10−12)