, f* g5 Y5 [# A; `5 { f, U o, D4 vCOVER Overlayed scanning tunneling and atomic force microscopy images N/ k! J3 @- f; Y! k: Q _0 V
of a single atom (width 1.3 nanometers): tunneling current (gray veil) and force - c" s" Z7 {6 W l* P5 V(colored surface) between a tungsten atom and a carbon monoxide molecule. The 2 m- r; m! h+ U+ {/ {
force shows a strong angular dependence and is attractive (blue minimum) in one / p" |* V( E9 `. ]
direction and repulsive (dark red crescent) in others. The angular dependence of + h" M/ y9 x3 B( b3 ?
single chemical bonds determines the shape of molecules and crystals. See page 2 S: g3 h, a' X6 z7 ^444. - q K) u2 X2 [' j
Image: Joachim Welker, University of Regensburg ( b4 A5 G+ P3 g$ m( e* a