Kofman V, Witlox M J A, Bouwman J, Ten Kate I L, Linnartz H
Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL 2300 RA Leiden, The Netherlands.
Fine Mechanical Department, Leiden Institute for Physics Research (LION), Niels Bohrweg 2, NL 2333 CA Leiden, The Netherlands.
Rev Sci Instrum. 2018 May;89(5):053111. doi: 10.1063/1.5027079.
This article describes a new, multi-functional, high-vacuum ice setup that allows to record the in situ and real-time spectra of vacuum UV (VUV)-irradiated non-volatile molecules embedded in a low-temperature (10 K) amorphous solid water environment. Three complementary diagnostic tools-UV-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopy and temperature-programmed desorption quadrupole mass spectrometry-can be used to simultaneously study the physical and chemical behavior of the organic molecules in the ice upon VUV irradiation. The setup is equipped with a temperature-controlled sublimation oven that enables the controlled homogeneous deposition of solid species such as amino acids, nucleobases, and polycyclic aromatic hydrocarbons (PAHs) in ice mixtures prepared from precursor gases and/or liquids. The resulting ice is photo-processed with a microwave discharge hydrogen lamp, generating VUV radiation with a spectral energy distribution representative for the interstellar medium. The characteristics, performance, and future potential of the system are discussed by describing three different applications. First, a new method is introduced, which uses broadband interference transmission fringes recorded during ice deposition, to determine the wavelength-dependent refractive index, n, of amorphous solid water. This approach is also applicable to other solids, pure and mixed. Second, the UV-vis and FTIR spectroscopy of an VUV-irradiated triphenylene:water ice mixture is discussed, monitoring the ionization efficiency of PAHs in interstellar ice environments. The third and final example investigates the stability of solid glycine upon VUV irradiation by monitoring the formation of dissociation products in real time.
本文介绍了一种新型的多功能高真空制冰装置，该装置能够记录嵌入低温（10K）非晶态固态水环境中的真空紫外（VUV）辐照非挥发性分子的原位实时光谱。三种互补的诊断工具——紫外可见（UV-vis）光谱、傅里叶变换红外（FTIR）光谱和程序升温脱附四极杆质谱——可用于同时研究冰中有机分子在VUV辐照下的物理和化学行为。该装置配备了一个温度可控的升华炉，能够将氨基酸、核碱基和多环芳烃（PAHs）等固体物质均匀地沉积到由前驱体气体和/或液体制备的冰混合物中。生成的冰用微波放电氢灯进行光处理，产生具有代表星际介质光谱能量分布的VUV辐射。通过描述三种不同的应用来讨论该系统的特性、性能和未来潜力。首先，介绍了一种新方法，该方法利用冰沉积过程中记录的宽带干涉透射条纹来确定非晶态固态水的波长相关折射率n。这种方法也适用于其他纯的和混合的固体。其次，讨论了VUV辐照的三亚苯：水冰混合物的UV-vis和FTIR光谱，监测星际冰环境中PAHs的电离效率。第三个也是最后一个例子通过实时监测解离产物的形成来研究VUV辐照下固体甘氨酸的稳定性。
