Identifying isomers of carbon-dioxide clusters by laser-driven Coulomb explosion

Clusters usually exhibit unique structures as an intermediate form of matter. However, their structures are still difficult to be determined with available experimental techniques. There are many structure distinct isomers for carbon-dioxide clusters. Here we report an experimental and theoretical joint study to determine the structures of the lowest-energy isomers. In the experiment, we exploded carbon-dioxide clusters by laser-driven multiple ionization and obtained precise momentum vectors of explosion fragments for each explosion channel. In the theory, we calculated low-energy structures of carbon-dioxide clusters and simulated their explosion dynamics. In comparison with the momentum vectors of explosion fragments, the lowest-energy isomers were identified for carbon-dioxide dimers, trimers, and tetramers.

Figure 1

Predicted low-energy structures of ${\mathrm{CO}}_2$ dimers, trimers, and tetramers.

Figure 2

Time-of-flight mass spectra of a supersonic carbon-dioxide beam irradiated by 780 nm, 25 fs laser pulses at an intensity of $5\times {10}^{14}$ W/$\mathrm{cm}{}^2$.

Figure 3

Kinetic energy release distribution for the ions produced in the explosion channels of carbon-dioxide dimers, trimers, and tetramers. Black lines represent experimental data and red lines represent the fitting data with Gaussian function.

Figure 4

Newton diagram for Coulomb explosion of carbon-dioxide trimers and tetramers (see text).