Role of the Gouy phase in the coherent phase control of the photoionization and photodissociation of vinyl chloride

We demonstrate theoretically and experimentally that the Gouy phase of a focused laser beam may be used to control the photoinduced reactions of a polyatomic molecule. Quantum mechanical interference between one- and three-photon excitation of vinyl chloride produces a small phase lag between the dissociation and ionization channels on the axis of the molecular beam. Away from the axis, the Gouy phase introduces a much larger phase lag that agrees quantitatively with theory without any adjustable parameters

Exploration of Novel Botanical Insecticide Leads: Synthesis and Insecticidal Activity of β‑Dihydroagarofuran Derivatives

The discovery of novel leads and new mechanisms of action is of vital significance to the development of pesticides. To explore lead compounds for botanical insecticides, 77 β-dihydroagarofuran derivatives were designed and synthesized. Their structures were mainly confirmed by ¹H NMR, ¹³C NMR, DEPT-135°, IR, MS, and HRMS. Their insecticidal activity was evaluated against the third-instar larvae of Mythimna separata Walker, and the results indicated that, of these derivatives, eight exhibited more promising insecticidal activity than the positive control, celangulin-V. Particularly, compounds <b>5.7</b>, <b>6.6</b>, and <b>6.7</b> showed LD₅₀ values of 37.9, 85.1, and 21.1 μg/g, respectively, which were much lower than that of celangulin-V (327.6 μg/g). These results illustrated that β-dihydroagarofuran ketal derivatives can be promising lead compounds for developing novel mechanism-based and highly effective botanical insecticides. Moreover, some newly discovered structure–activity relationships are discussed, which may provide some important guidance for insecticide development

Coherent Control of the Photoionization of Pyrazine

Most attempts to control the absorption of resonant light by quantum mechanical interference have been limited to atoms and small molecules with specialized state configurations and selection rules. Here we illustrate experimentally the possibility of creating laser-induced transparencies in complex molecular systems. Our approach takes advantage of the nonadiabatic excited-state dynamics characteristic of polyatomic molecules. Specifically, we show that it is possible to construct femtosecond pulses using a genetic algorithm to suppress the ionization of isolated pyrazine molecules at a prespecified time. The data suggest that transparency is achieved by localization of a wave packet in a region of the coupled S₁/S₂ potential energy surfaces, where a vertical transition to the ionic state is energetically forbidden. This approach is general and does not require prior knowledge of the molecular Hamiltonian