The dynamics of the reactions of translationally energetic H atoms with BrCN, ClCN, and (CN)(2) was studied by determining both the rotational state distribution and the translational energy disposition of the CN product ground vibrational level. The reaction was carried out using H atoms with a most probable translational energy of 92 kJ mol(-1). The CN radical was monitored by time- and frequency-resolved absorption spectroscopy using the CN red system (A (2)Pi <-- X (2)Sigma) (2,0) band near 790 nm. Sub-Doppler resolution spectroscopy was used to determine the initial translational temperature of the CN(0,J) product. The fraction of the available reaction exothermicity that appeared as CN(0) rotational energy, f(R), for H+XCN --> HX+CN was 0.034 +/- 0.006, 0.061 +/- 0.02, and 0.13 +/- 0.007, for X=Br, Cl, and CN, respectively. Likewise, the fraction of the available reaction exothermicity that appeared as relative product translational energy, f(T), was 0.52 +/- 0.25, 0.52 +/- 0.20, and 0.59 +/- 0.05, for X=Br, Cl, and CN, respectively. The absolute reaction cross sections for the H+XCN --> HX+CN reactions were also measured to be 0.03, 0.02, and 0.3x10(-16) cm(2) for X=Br, Cl, and CN, respectively. (C) 2000 American Institute of Physics. [S0021-9606(00)01115-6].