Time-dependent correlation function based methods to study optical spectroscopy involving electronic transitions can be traced back to the work of Heller and coworkers. This intuitive methodology can be expected to be computationally efficient and is applied in the current work to study the vibronic absorption, emission, and resonance Raman spectra of selected organic molecules. Besides, the "non-standard" application of this approach to photoionization processes is also explored. The application section consists of four chapters as described below. In Chapter 4, the molar absorptivities and vibronic absorption/emission spectra of perylene and several of its N-substituted derivatives are investigated. By systematically varying the number and position of N atoms, it is shown that the presence of nitrogen heteroatoms has a negligible effect on the molecular structure and geometric distortions upon electronic transitions, while spectral properties are more sensitive: In particular the number of N atoms is important while their position is less decisive. Thus, N-substitution can be used to fine-tune the optical properties of perylene-based molecules. ...

The transition from smallholders to large farms in developing countries has attracted rising attention. We present an integrated theoretical framework that examines the dynamics and welfare implications of this transition for rural residents, urban consumers, and society. Unlike previous studies, our framework focuses on the transition and upgrade of livestock farms as opposed to the crop sector and is more realistic by allowing for the coexistence of smallholders and large farms. Our application focuses on hog farming in China, which is arguably the world' largest livestock sector. Our results show that the transition to larger hog farms leads to a persistent welfare loss for independent and employed smallholders (rural residents), but the losses are outweighed by larger welfare gains enjoyed by urban consumers. The income effect dominates in the welfare changes of smallholders, who first benefit but then suffer from the transition by working for large farms. Despite the labor efficiency losses faced by large farms, their credit and technology advantages sustainably increase total pork production and lower retail pork prices, thereby enhancing total social welfare. The transition can generate welfare gains for rural residents, urban consumers, and society when smallholders are allowed to exit hog farming. The proposed integrated framework provides a novel theoretical perspective and analytical tool for examining the transition in the agricultural sector. Our framework is characterized by its generality and its ability to capture the dynamics and welfare effects of the transition across various agricultural contexts and regions.

Agricultural water pollution from the livestock industry is a growing concern in China and globally. As opposed to size-based regulations targeting larger facilities in the United States, China's regulations are place-based in nature. Since 2014, China classified eight urban provinces in the southeast as a Development Control Zone (DCZ), which prohibits new hog facility construction and encourages hog farms to relocate to other regions. Leveraging a novel, doubly-robust identification strategy, synthetic difference-in-differences, and the place-based nature of China's environmental regulations, we provide one of the first systematic analyses of the impacts of the regulations on the county-level hog and sow inventories, especially revealing heterogeneous responses. Our results show that, on average, the regulations led to a 14.7% reduction in hog inventories after the environmental regulations in the counties in DCZ provinces, mainly resulting from hog farm closures impacting over 20 million head of pigs and causing U.S.$5.62 billion loss in hog sectoral revenue. The treatment effects vary substantially both within and across DCZ provinces: wealthier urban provinces such as Zhejiang experienced a reduction in hog and sow inventories of around 40%, and counties upstream of big cities or those designated as main hog counties saw steeper declines as well.