\begin{table}%t1 \caption{\label{lifetime}Calculated and experimental lifetimes for Nb~II~levels of the 4d$^3$5p~configuration.} \begin{tabular}{ccccccr} \hline\hline & & \multicolumn{3}{c}{Theory} & \multicolumn{2}{c}{Experiment} \\ Desig.\tablefootmark{a} & $E$\tablefootmark{a} & $\tau$(ns) & $\tau$(ns) & $\tau$(ns) & $\tau$(ns) & $\tau$(ns) \\ & (cm$^{-1}$) & {HFR(A)} & HFR(B) & & & \\ & & this work & this work & previous & this work & previous \\ \hline \noalign{\smallskip} 4d$^3$($^4$F)5p $^5$G$_2^\circ$ & 33 351.09 & 5.0 & 5.6 & & & 5.9(4)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$G$_3^\circ$ & 33 919.24 & 4.9 & 5.5 & 5.16\tablefootmark{b}, 6.53\tablefootmark{c} & & 6.2(3)\tablefootmark{d}, 5.8(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$G$_4^\circ$ & 34 632.03 & 4.7 & 5.3 & & & 5.8(3)\tablefootmark{d}, 5.5(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$D$_1^\circ$ & 34 886.35 & 5.1 & 5.9 & & 5.6(3) & 5.5(3)\tablefootmark{d}, 5.7(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$G$_5^\circ$ & 35 474.20 & 4.6 & 5.2 & & & 5.3(3)\tablefootmark{d}, 5.3(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$D$_2^\circ$ & 35 520.82 & 4.8 & 5.7 & & 5.5(3) & 5.7(3)\tablefootmark{d}, 5.7(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$G$_6^\circ$ & 36 455.46 & 4.4 & 5.0 & & & 5.0(3)\tablefootmark{d}, 5.1(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$D$_3^\circ$ & 36 553.24 & 4.2 & 5.0 & 4.67\tablefootmark{b}, 5.60\tablefootmark{c} & & 5.0(3)\tablefootmark{d}, 5.0(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$F$_1^\circ$ & 36 731.81 & 4.0 & 4.7 & & & 4.7(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$F$_2^\circ$ & 36 962.77 & 4.0 & 4.7 & & & 4.7(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$D$_0^\circ$ & 37 298.24 & 2.3 & 2.7 & & 2.6(2) & 3.1(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$F$_3^\circ$ & 37 376.90 & 3.9 & 4.6 & & & 4.7(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$D$_1^\circ$ & 37 480.08 & 2.4 & 2.7 & & & 3.1(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$F$_4^\circ$ & 37 528.38 & 3.8 & 4.4 & & & 4.6(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$D$_2^\circ$ & 37 797.32 & 2.6 & 2.8 & & 2.7(2) & 3.2(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$F$_5^\circ$ & 38 024.34 & 3.9 & 4.6 & & & 4.6(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$D$_3^\circ$ & 38 216.39 & 2.7 & 3.0 & & & 3.4(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^5$D$_4^\circ$ & 38 291.25 & 2.6 & 3.0 & & & 3.3(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$G$_3^\circ$ & 38 684.96 & 4.5 & 5.1 & & & 5.0(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$F$_2^\circ$ & 38 984.39 & 6.8 & 7.3 & & & 7.3(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$G$_4^\circ$ & 39 335.27 & 4.5 & 5.1 & & & 5.1(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$F$_3^\circ$ & 39 779.92 & 6.3 & 6.9 & & & 6.8(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$G$_5^\circ$ & 40 103.61 & 4.4 & 5.0 & & 5.1(3) & 5.2(3)\tablefootmark{e} \\ 4d$^3$($^4$F)5p $^3$F$_4^\circ$ & 40 561.02 & 5.8 & 6.3 & & & 6.4(3)\tablefootmark{e} \\ 4d$^3$($^4$P)5p $^3$P$_2^\circ$ & 41 710.14 & 7.9 & 8.4 & & 8.5(7) & \\ 4d$^3$($^4$P)5p $^3$P$_1^\circ$ & 42 132.65 & 6.5 & 7.2 & & 7.2(5) & \\ 4d$^3$($^4$P)5p $^5$D$_0^\circ$ & 42 596.55 & 6.3 & 7.2 & & 7.5(7) & \\ 4d$^3$($^4$P)5p $^5$D$_2^\circ$ & 43 290.34 & 6.9 & 7.3 & & 7.5(4) & \\ 4d$^3$($^2$P)5p $^1$D$_2^\circ$ & 43 618.39 & 6.4 & 6.7 & & 6.7(3) & \\ 4d$^3$($^2$P)5p $^3$D$_1^\circ$ & 43 649.19 & 8.4 & 8.1 & & 7.2(4) & 12.8(3)\tablefootmark{e} \\ 4d$^3$($^4$P)5p $^5$D$_3^\circ$ & 43 887.08 & 5.9 & 6.3 & & 5.7(5) & \\ 4d$^3$($^4$P)5p $^5$D$_1^\circ$ & 44 066.67 & 5.8 & 6.7 & & 6.4(5) & 5.3(3)\tablefootmark{e} \\ 4d$^3$($^4$P)5p $^3$P$_0^\circ$ & 44 285.94 & 6.6 & 7.5 & & 7.0(5) & \\ 4d$^3$($^2$P)5p $^3$D$_2^\circ$ & 44 924.60 & 5.9 & 6.6 & & 6.2(3) & \\ 4d$^3$($^4$P)5p $^5$D$_4^\circ$ & 44 970.71 & 5.1 & 5.8 & & 5.2(5) & \\ 4d$^3$($^2$P)5p $^3$D$_3^\circ$ & 45 802.47 & 4.9 & 4.6 & & 4.6(3) & \\ 4d$^3$($^2$H)5p $^3$H$_6^\circ$ & 48 770.84 & 4.5 & 3.7 & & & 4.2(3)\tablefootmark{e} \\[2pt] \hline \end{tabular} \tablefoot {\tablefoottext{a}{From Ryabtsev et~al. (\cite{ryabtsev});} \tablefoottext{b}{from Beck \& Datta (\cite{beck}): length form;} \tablefoottext{c}{from Beck \& Datta (\cite{beck}): velocity form;} \tablefoottext{d}{from Salih \& Lawler (\cite{salih});} \tablefoottext{e}{from Hannaford et~al. (\cite{hannaford}). $A(B)$ is written for $A \pm B$.}} \end{table}