\\ Species Tag:        &   41011 & Name:&  K41-atom
\\ Version:            &       1 & &$^2$S$_{1/2}$ ground state
\\ Date:       &  Dec. 2014     & & $^2$P$_J$ $J$ = $\frac{1}{2}$,$\frac{3}{2}$
\\ Contributor:&  B. J. Drouin  & &
\\             &                 & &
\\ Lines Listed:       &      11 & Q(300.0)=&        7.9998
\\ Freq. (GHz) $<$     & 7500000 & Q(225.0)=&        7.9997
\\ Max. J:             &       1 & Q(150.0)=&        7.9996
\\ LOGSTR0=            &   -99.0 & Q(75.00)=&        7.9982
\\ LOGSTR1=            &    -5.0 & Q(37.50)=&        7.9984
\\ Isotope Corr.:      &  -1.167 & Q(18.75)=&        7.9968
\\ Egy. (cm$^{-1}$) $>$& 0.0000  & Q(9.375)=&        7.9935
\\ $\mu_e$ = & 6.3768            & A=&
\\ $\mu_m$ = & 2.0               & B=&
\headend

The atomic potassium line at has been measured to a precision of 0.001 
Hz 
1. Chan et al. 1970. See archived line file for precise frequency.

The transitions (a.k.a. $D_1$ and $D_2$ lines) to the $^2$P$_J$ levels are measured with Lamb-dip spectroscopy,

2. S. Falke, E. Tiemann, C. Lisdat, H. Schnatz, G. Grosche, 2006, Phys. Rev. A 74, 032503.

All positions of the $^2$S$_{1/2}$-$^2$P$_{1/2}$ multiplet were reported in 2, however only the hyperfine free center and a single component of the $^2$S$_{1/2}$-$^2$P$_{3/2}$ multiplet were reported.  For determination of the equivilent SPFIT operators, the $A_{3/2}$ and $B_{3/2}$ constants reported in [2] were used with the Casimir expression to determine calculated line centers for the remaining 5 transitions, these are used in the fit and artificially reduce the reduced rms.  The fit includes a fixed value of a fictitious (and extremely large) value of the $\lq$ rotational' constant which serves to remove non-zero $N$ quanta from the prediction.

The dipole moment for the $^2$S$_{1/2}$-$^2$P$_{J}$ transitions of $^{39}$K was assumed to be that of the $^2$S$_{1/2}$-$^2$P$_{3/2}$ transition given by U.I. Safranova and M.S. Safranova, Phys. Rev. A 78, 052504 2008. the value given therein, 5.7939, was converted to Debye from atomic units (14.726 D) and then an empirically determined spherical harmonic scaling factor of $\sqrt(16/3)$ was factored out of the input value for entry into the .int file (6.3768 D).  This value reproduces the lifetime ($\tau$ = 26.5 ns) of the $^2$S$_{1/2}$-$^2$P$_{3/2}$ state well, Wang et al. J. Chem. Phys. 106(19):7899-7912, 1997 report a value of 26.37(5) ns.  The other transition gives a lifetime 2$\times$ longer than reported, presumably due to the different degeneracies of the states.