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This paper considers population transfer between eigenstates of a finite quantum ladder controlled by a classical electric field. Using an appropriate change of variables, we show that this setting can be set in the framework of adiabatic passage, which is known to facilitate ensemble control of quantum systems. Building on this insight, we present a mathematical proof of robustness for a control protocol-chirped pulse-practised by experimentalists to drive an ensemble of quantum systems from the ground state to the most excited state. We then propose new adiabatic control protocols using a single chirped and amplitude-shaped pulse, to robustly perform any permutation of eigenstate populations, on an ensemble of systems with unknown coupling strengths. These adiabatic control protocols are illustrated by simulations on a four-level ladder.

N 2 O removal was investigated in N 2 or air using 172 nm Xe 2 excimer lamps (50 or 300 mW/cm 2 ) without using any expensive catalysts. The residual amount of N 2 O and the formation ratios of products were measured as functions of photoirradiation time, N 2 O concentration, and O 2 concentration. N 2 O (100 ppm) was completely converted to N 2 and O 2 without NO x emission in N 2 at atmospheric pressure after 30 min photoirradiation using a high-power Xe 2 excimer lamp (300 mW/cm 2 ). 76% of N 2 O (100 ppm) was also converted to N 2 , O 2 , and HNO 3 in air (20% O 2 ) after 30 min photoirradiation using the high-power lamp. We concluded that N 2 O is dominantly decomposed by 172 nm photolysis in N 2 and by the O( 1 D) þ N 2 O reaction in air, where O( 1 D) atoms dominantly arise from the 172 nm photolysis of O 2 . The conversion of N 2 O in air increased more than twofold by decreasing the total pressure from atmospheric pressure to 20 kPa by suppressing the collisional quenching of O( 1 D) by N 2 and O 2 buffer gases. In a flow experiment, the conversion of N 2 O in N 2 was only 6 -18% in the total flow rate range of 0.1-1 L/min owing to the short residence time of N 2 O in the photolysis chamber.