Electronic movement flashing into view Numerous chemical processes begin with ionization: the ejection of an electron from a molecule. What happens in the immediate aftermath of that event? Kraus et al. explored this question in iodoacetylene by detecting and analyzing the spectrum of emitted high harmonics (see the Perspective by Ueda). They traced the migration of the residual positively charged hole along the molecular axis on a time scale faster than a quadrillionth of a second. They thereby characterized the capacity of a laser field to steer the hole's motion in appropriately oriented molecules. Science , this issue p. 790 ; see also p. 740

The optimized geometries, adiabatic electron affinities, and IR-active vibrational frequencies have been predicted for the long linear carbon chains HC(2n)H. The B3LYP density functional combined with the DZP basis set was used in this theoretical study. The computed physical properties are discussed. The predicted electron affinities form a remarkably regular sequence: 1.78 (HC(12)H), 2.08 (HC(14)H), 2.32 (HC(16)H), 2.53 (HC(18)H), 2.69 (HC(20)H), 2.83 (HC(22)H), and 2.95 eV (HC(24)H). The predicted structures display an alternating triple and very short single bond pattern, with the degree of bond alternation significantly less for the radical anions.

The optimized geometries, adiabatic electron affinities, vertical electron affinities, vertical electron detachment energies (for the anions), and IR-active vibrational frequencies have been predicted for the long linear carbon chains HC(2)(n)()(+1)H (n = 4-11). The B3LYP density functional combined with DZP and TZ2P basis sets was used in this theoretical study. These methods have been extensively calibrated versus experiment for the prediction of electron affinities (Chem. Rev. 2002, 102, 231). The computed physical properties are discussed and compared with the even carbon chains HC(2)(n)()H. The predicted electron affinities form a remarkably regular sequence: 2.12 eV (HC(9)H), 2.42 eV (HC(11)H), 2.66 eV (HC(13)H), 2.85 eV (HC(15)H), 3.01 eV (HC(17)H), 3.14 eV (HC(19)H), 3.25 eV (HC(21)H), and 3.35 eV (HC(23)H). These electron affinities are as much as 0.4 eV higher than those for analogous even carbon chains. The predicted structures display an intermediate cumulene-polyacetylene type of bonding, with the inner carbons appearing cumulenic and the outer carbons polyacetylenic.