VALD3 line lists contain a mandatory accuracy parameter for the oscillator strengths. This field is returned at beginning (2nd field) of the reference line of the long format extraction. Here are a few examples:

'Fe 1',       5166.2816,  -4.195,  0.0000,  4.0,  2.3992,  5.0, 1.600, 1.500, 1.310, 3.160,-6.280, 204.253, ...
'  LS                                                                           3d6.4s2 a5D'
'  LS                                                             3d6.(5D).4s.4p.(3P*) z7D*'
'FMW    N B+       Kurucz Fe I 2014Fe               7 K14      11 FMW       7 K14       7 K14       7 K14 ...
'Mg 1',       5167.3216,  -0.931,  2.7091,  0.0,  5.1079,  1.0,99.000,99.000,99.000, 7.990,-5.470, 729.23, ...
'  LS                                                          3s.3p                    3P*'
'  LS                                                              3s.4s                 3S'
'ATJL   E 0.037     CNO, Na 1, Mg 1:Mg              17 NIST10   18 ATJL     17 NIST10   17 NIST10   19 KP ...
'Fe 1',       5167.4879,  -1.118,  1.4849,  4.0,  3.8835,  3.0, 1.320, 1.250, 1.420, 6.750,-6.150, 281.253, ...
'  LS                                                                       3d7.(4F).4s a3F'
'  LS                                                             3d6.(5D).4s.4p.(3P*) z3D*'
'BWL    E 0.021    Kurucz Fe I 2014Fe               7 K14      11 BWL       7 K14       7 K14       7 K14 ...
'Fe 1',       5167.7176,  -2.814,  3.4149,  1.0,  5.8135,  2.0, 0.820, 1.260, 1.480, 8.020,-6.060,  -7.770, ...
'  LS                                                                       3d7.(2P).4s a1P'
'  LS                                                                            (4P)4p 3D*'
'K14               Kurucz Fe I 2014Fe               7 K14       7 K14       7 K14       7 K14       7 K14 ...
'Nd 2',       5167.9200,  -1.180,  0.5595,  6.5,  2.9580,  5.5, 1.110, 1.010, 1.380, 0.000, 0.000,   0.000, ...
'  LS                                                  4f4.(5I).6s                       4I'
'                                                                                         *'
'HLSC   E 0.04     Wisconsin REE exNd+             12 HLSC     12 HLSC     12 HLSC     12 HLSC     12 HLSC ...

The accuracy filed consists of accuracy flag and optional parameter. Accuracy flag values are:

' ' or '_' ... no value

'N' ... quality class (NIST)

• An estimated accuracy is listed for each transition strength, indicated by a code letter as given in the list below:

  AAA ≤ 0.3%
  

  AA ≤ 1%
  

  A+ ≤ 2%
  

  A ≤ 3%
  

  B+ ≤ 7%
  

  B ≤ 10%
  

  C+ ≤ 18%
  

  C ≤ 25%
  

  D+ ≤ 40%
  

  D ≤ 50%
  

  E > 50%.
  

'E' ... absolute error in dex

'C' ... cancellation factor

• Cancellation factor (CF) is defined as follows. Calculations of the line transition probability are made by summation of contributions of eigenvector components of wave functions of the lower and upper states that come with different signs. All positive and negative contributions are summed separately in partial sums S+ and S−, so that the line strength is given by S = (S+) + (S−). Then CF is defined as CF = [(S+) − abs(S−)]/[(S+) + abs(S−)]. Thus, CF ends up in the range between [−1, 1], and “strong cancellation” occurs when |CF| is close to zero.
  

'P' ... predicted line