The interaction of excited atoms and few-cycle laser pulses

Abstract

This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrödinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and measure the ionisation rate as the a function of different steady-state populations in the fine structure of the target state which shows significant ionisation rate dependence on populations of spin-polarised states. The physical mechanism for this effect is unknown.

Metastable noble gas atoms in strong-field ionization experiments

“…Characterization experiments have also been performed, for example the effects of polarization of the ionizing beam on the ionization rate of helium and neon [100] and the effects of atomic shell structure on NSDI [61] . Investigation the strong-field ionization of metastable neon (Ne * ) was recently performed by Calvert et al [101] . This work was pursued for a number of reasons.…”

“…The optical pumping process was modelled by solving the optical Bloch equations (OBEs) in the rotating wave approximation (RWA) [101] . The OBEs semiclassically describe the evolution of the internal states of an atom in the presence of an external field, including the atomic state coherences and spontaneous decay effects.…”

“…This was modelled by using Jones matrix formalism for the transformation of Figure 16. Figure adapted from Calvert et al [101] . Population fraction of m j sublevels in Ne * atoms being pumped by σ − circularly polarized light with the parameters given in Table 1.…”

“…For σ + pump light, the plot is similar except with the signs of the m j states reversed. [101] . The modelled change in the m j state fraction of a 3 P 2 Ne atom beam as the fast axis of a quarterwave plate is rotated around the pass axis of a linear polarizer.…”

Взаимодействие Интенсивных Предельно Коротких Импульсов С Квантовыми Объектами

“…С другой сторо-ны, понятие резонансных переходов также оказывается неприменимым ввиду краткости импульса и соответ-ственно малого времени раскачки отвечающих объек-ту осцилляторов. В этих условиях лучшее описание взаимодействия реализуется при численном решении нестационарного уравнения Шредингера для волновой функции объекта [9]. Задачей данного сообщения слу-жит анализ простой модели взаимодействия квантового объекта (для определенности атома) с предельно интен-сивным и коротким импульсом излучения, в которой не используется ограничение числа уровней.…”