Laser photolysis experiments on carboxymethylated chitin derivatives, such as carboxymethyl chitin (CM-chitin) and carboxymethyl chitosan (CM-chitosan), in aqueous solution by a 248 nm excimer laser were carried out for the first time. The transient absorption spectra of photolyzed CM-chitin or CM-chitosan solutions revealed a strong band with the maximum at 720 nm, which was assigned to the hydrated electron (e(aq)(-)). In the presence of argon, the e(aq)(-) decays by reacting with CM-chitin or CM-chitosan, and the rate constants are (6.1 +/- 0.1) x 10(7) M-1 s(-1) and (3.7 +/- 0.1) x 10(7) M-1 s(-1), respectively. Long-lived radicals with relatively weak absorption intensity were detected in the near-UV region. The absorption band was not notably characteristic and showed only an increasing absorption toward shorter wavelengths. It is similar to the signal of (CM)-C-.-chitin or (CM)-C-.-chitosan macroradicals formed by the reaction of CM-chitin or CM-chitosan with an OH. radical. It was assigned to (CM)-C-.-chitin(-) or (CM)-C-.-chitosan(-) macroradicals formed by e(aq)(-) + CM-chitin or CM-chitosan reaction. CM-chitin aqueous solutions were further examined by pulse radiolysis in order to confirm the site of the long-lived radical.