The bound excited np3 2D terms of Si-, Ge-, and Sn- have been investigated with a combination of single- and multiphoton tunable infrared laser experiments. The binding energies of the two J=3/2 and J=5/2 fine-structure levels were found to be 0.527 234(25) and 0.525 489(20) eV, respectively for Si-, 0.401 44(10) and 0.377 27(6) eV for Ge-, and 0.397 617(15) and 0.304 635(15) eV for Sn-. These results constitute improvements in accuracy over previous experimental term energies of up to four orders of magnitude and further provide experimental values for the 2D fine-structure splittings: 14.08(20), 192.6(9), and 749.95(15) cm-1 for Si-, Ge-, and Sn-, respectively. In addition, the photodetachment thresholds of the ionic 4S3/2 ground states have been reinvestigated. This resulted in improved electron affinities of 1.262 119(20), 1.389 521(20), 1.232 712(15), and 1.112 067(15) eV for C-, Si-, Ge-, and Sn-, respectively. Various attempts towards an observation of the very weakly bound C-(2D) and Si-(2P) terms remain unsuccessful.