Laser-Induced Phase Transitions in Gas-Phase Suspended Molecular Nanoparticles

实验和计算机化学研究气相悬浮H2O和D2 O纳米粒子的熔化和蒸发。通过使用红外发射激光源来实现初始处于热平衡的颗粒的加热。HDO将作为颗粒中液相存在的指示剂。一种用于生成由不同同位素组成的幔核颗粒和层状颗粒的新技术，结合激光加热和灵敏的FTIR检测，将首次获得水纳米颗粒的位置相关结构信息。特别的努力将被导向上的准液体层（QLL）的厚度，结构和温度依赖性的粒子的调查。QLL决定了粒子的蒸汽压;量子效应的作用将成为焦点。其他努力致力于研究分子自扩散的颗粒的过程。通过使用激光诱导的爆炸性颗粒蒸发，每个颗粒具有2至100个分子的热平衡中的较小尺寸的水簇的目标。一个银行的计算机代码用于模拟水分子团簇的结构和动力学将适用于尺寸高达n = 1000个分子，并平行于实验程序开发更大的颗粒。程序采用分子动力学、路径积分蒙特卡罗等方法。预期的结果应该有重大意义的基础水的研究，大气和天体化学的应用，以及纳米工程的分子纳米粒子。

Experimental and computer-chemical investigation of melting and vaporisation of gas-phase suspended H20 and D2O nanoparticles is proposed. The heating of the particles being initially in thermal equilibrium will be realized by use of infrared-emitting laser sources. HDO will act as an indicator for presence of the liquid phase in the particles. A new technique for generation of mantle-core particles and layered particles composed of different isotopomers, combined with laser heating and sensitive FTIR detection, will allow to get site-dependent structure information for water nanoparticles for the first time. Special efforts will be directed on the investigation of thickness, structure and temperature dependence of the quasi-liquid-layer (QLL) on the particles. The QLL determines the vapour pressure of the particles; the role of quantum effects will be on focus. Other efforts are addressed to study processes of the particles as molecular self-diffusion. Smaller sizes of water clusters in thermal equilibrium with 2 to 100 molecules per particle are aimed for by use of laser-induced explosive particle vaporisation. A bank of computer codes for simulating structure and dynamics of water clusters will be applied for sizes up to n = 1000 molecules and developed for bigger particles parallel to the experimental program. The codes apply Molecular Dynamics, Path Integral Monte Carlo and other methods. The expected results should have major importance to basic water research, to atmospheric and astro-chemical applications as well as to nanoengineering of molecular nanoparticles.