Fig. 1. The Coulomb explosion image of NO₂ (inset) and surface plot showing the momentum distribution of N ^q+ and O ^q+ ions (75% q=2 and 25% q=3). This distribution contains 500,000 laser pulses, each centered at 800 nm, with a pulse width of 100 fs and linearly polarized (horizontal in the inset) with a peak intensity of 10¹⁵ W/cm². The vertical distribution is composed of N ^q+ ions while the distribution parallel to the polarization axis is a mixture of both N ^q+ and O ^q+ ions.

Fig. 2. This figure explains how to read a correlation image. The concentric circles and spokes in the upper left panel divide the momentum distribution image (the same as that displayed in the inset of Fig. 1) into sectors. The grey arrow indicates labeled ions (i.e., a subset of ions with a narrow momentum distribution moving downward, 6 o’clock); the white arrows indicate the correlated sectors (ions moving toward 2 and 10 o’clock). The right panel shows the correlation image for the Coulomb explosion where all three atomic ions are ejected simultaneously. This image shows the momenta of the charges ejected simultaneously. The grey (white) arrows indicate the final momenta of the labeled (correlated) charges. The correlation image in the lower left panel is the difference between averaging only those frames that have a nonzero count in the labeled sector and the average of all 500,000 frames.

Fig. 3. Two correlation images for the Coulomb explosion of CO₂ taken under the same conditions as Fig. 1. We label O ion moving toward 3 o’clock in the left image and those moving toward 6 o’clock in the right image. We isolate linear explosion events on the left and bent events on the right.

Fig. 4. Two correlation images for NO₂ taken from the same data set as Fig. 1 showing a sequential dissociation-channel (left) and a simultaneous dissociation-channel. The sequential channel involves an explosion of NO₂ into NO+O ions followed by the explosion of the NO ion. Pictured on the left is the explosion of NO. The explosion dynamics is asymmetric, the center of mass of the two correlated charges is not the center of the image.