hence the $\{ 5-4 \}$ and $\{ 4-3 \}$ intervals.

\(a) (b)

The average value for the $\{ 5-4 \}$ interval is 251.031(20) MHz, as listed in Table \[t3\]. This was obtained from a set of 27 independent measurements with a standard deviation of 21 kHz. We concentrated on this interval because two of the values reported in the literature, 251.092(2) MHz from Ref. [@GDT03] and 251.000(20) from Ref. [@TAW88], differ by $4.5
\sigma$. The more recent measurement of the two [@GDT03] was done using a frequency comb. An earlier measurement from our laboratory using the AOM locking technique [@DAN05] yielded a result of 251.037(6) MHz, which was consistent with the earlier value at the $1.5
\sigma$ level, but totally inconsistent with the frequency-comb result (difference of $9\sigma$). Our current value vindicates our earlier result since it is consistent with the work in Ref. [@TAW88] but not with the frequency-comb result.

  $\{ 5-4 \} $ Interval   $\{ 4-3 \} $ Interval    Reference
  ----------------------- ----------------------- -----------
  251.031(20)             201.260(20)              This work
  251.037(6)              201.266(6)               [@DAN05]
  251.092(2)              201.287(1)               [@GDT03]
  251.000(20)             201.240(20)              [@TAW88]

  : Comparison of measurements of hyperfine intervals in the $6P_{3/2}$ state of $^{133}$Cs to previous results. All values in MHz.

\[t3\]

For 