Photoionization of excited atomic states: Photoelectron anisotropy for N 2p23p1/22

The two-photon-resonant, three-photon (2+1) ionization spectrum of atomic nitrogen produced by photodissociation of nitrous oxide has been determined between 2692 and 2687 Å, and shows two peaks corresponding to the N ${}_{}{}^2{}_{}{}^{}\mathrm{}_{1/2}^{}{}_{}{}^{}$←${\mathrm{}}^2$D°${\mathrm{}}_{3/2}$,5/2 transitions. The photoelectron spectrum for (2+1) ionization via the ${}_{}{}^2{}_{}{}^{}\mathrm{}_{1/2}^{}{}_{}{}^{}$ state displays a single ${\mathrm{N}}^{+}$ photoelectron peak corresponding to the production of the ${}_{}{}^3{}_{}{}^{}\mathrm{P}$ ground state. The photoelectron angular distribution following ionization via the ${}_{}{}^2{}_{}{}^{}\mathrm{}_{1/2}^{}{}_{}{}^{}$←${\mathrm{}}^2$D°${\mathrm{}}_{5/2}$ transition shows a distinct minimum along the polarization axis of the laser light (β=-0.2±0.1). Implications of this anisotropy for the relative dipole amplitudes into the different ɛs and ɛd ionization channels are discussed.