Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)

Hawkins, Steve; Kumi, George; Malyk, S.; Reisler, H.; Wittig, C.

doi:10.1016/j.cplett.2005.01.049

Cited by 17 publications

(31 citation statements)

References 26 publications

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“…These experiments show the existence of three ordered structures in the monolayer range in dependence on temperature and coverage. But there is still a controversial discussion whether the water adsorption on the defect-free MgO(1 0 0) surface is molecular or dissociative [15].…”

Section: Introductionmentioning

confidence: 99%

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Jug¹,

Heidberg²,

Bredow³

2007

Surface Science

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Section: Introductionmentioning

confidence: 99%

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Jug¹,

Heidberg²,

Bredow³

2007

Surface Science

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“…The three-tier UHV chamber was described previously. 11,13,16 It is equipped for Fourier transform infrared (FTIR) spectroscopy, temperature programmed desorption (TPD), 11 and the laserinitiated ablation experiments reported herein. Figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…After the chamber reached base pressure, the substrate was annealed to 600 K in oxygen to remove oxygen vacancies and contaminants. 11,33 A surface holder that was used previously for FTIR and TPD experiments 13,16 was modified to reduce temperature gradients. The substrate was attached to a copper plate (14 mm " 10 mm " 0.3 mm) and secured by folding the edges of the plate over it.…”

Section: Methodsmentioning

confidence: 99%

“…10 Recent research with ASW and ASW/CO 2 has addressed the roles of sample morphology and its temperature variation, species segregation, and explosive boiling (phase explosion). [11][12][13][14][15][16][17][18][19][20] Pulsed infrared radiation (10 ns duration, 3424 cm -1 ) creates OH stretch excitation that converts to heat on a ps time scale. 4 Broad absorption spectra of ASW, crystalline ice, and liquid water ensure efficient excitation in samples whose character changes throughout the pulse.…”

Section: Introductionmentioning

confidence: 99%

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Amorphous Solid Water (ASW): Pulsed Laser Ablation of ASW/CO₂ Thin Films

et al. 2011

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Thin films comprised of 400 -500 monolayers (ML) of either amorphous solid water (ASW) or ASW/CO 2 mixtures are grown atop a MgO(100) substrate under ultrahigh vacuum conditions. Samples are irradiated at an infrared frequency of 3424 cm -1 , which lies within the broad OH stretch band of condensed water. Ablation is achieved using 10 ns pulses whose energy (< 2.7 mJ) is focused to a beam waist of approximately 0.5 mm. By using a time-of-flight mass spectrometer to monitor ablated material, excellent single-shot detection is demonstrated. This capability is essential because, in general, the first infrared pulse can induce irreversible changes throughout the irradiated volume. With ASW/CO 2 samples, CO 2 is released preferentially. This is not surprising in light of the metastability of the samples. Indeed, repeated irradiation of the same spot can rid the sample of essentially all of the CO 2 in as little as a few pulses, whereas only 10-20 ML of H 2 O are removed per pulse. The influence of the substrate is profound. It cools the sample efficiently because the characteristic time for heat transfer to the substrate is much less than the infrared pulse duration. This creates temperature gradients, thereby quenching processes such as explosive boiling (phase explosion) and the heterogeneous nucleation of cavities that take place at lower depths in significantly thicker samples, i.e., with sufficient inertial confinement. This efficient quenching accounts for the fact that only 10-20 ML of H 2 O are removed per pulse. The presence of small protonated water cluster ions in the mass spectra is interpreted as evidence for the trivial fragmentation mechanism examined assiduously by Lewis and coworkers. Mixed samples such as ASW/CO 2 , where species segregation plays a pivotal role, add interesting and potentially useful dimensions to the ablation phenomenon.

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“…(Öberg et al 2010), overall ice structure and physical behavior (Bossa et al 2012(Bossa et al , 2013Collings et al 2005;Hawkins et al 2005;Kumi et al 2006;Malyk et al 2007). The complex interplay between water molecules and charged small species embedded has been studied extensively using theoretical methods (Park & Woon 2004a,b;Woon 2004, and references therein).…”

Section: Low Concentration Regime (Pah:h 2 O < 1:1000)mentioning

confidence: 99%

Photochemistry of PAHs in cosmic water ice

Cuylle

Allamandola

Linnartz

2014

A&A

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Context. Observations and models show that polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the interstellar medium. Like other molecules in dense clouds, PAHs accrete onto interstellar dust grains, where they are embedded in an ice matrix dominated by water. In the laboratory, mixed molecular ices (not containing PAHs) have been extensively studied using Fourier transform infrared absorption spectroscopy. Experiments including PAHs in ices have started, however, the concentrations used are typically much higher than the concentrations expected for interstellar ices. Optical spectroscopy offers a sensitive alternative. Aims. We report an experimental study of the effect PAH concentration has on the electronic spectra and the vacuum UV (VUV) driven processes of PAHs in water-rich ices. The goal is to apply the outcome to cosmic ices. Methods. Optical spectroscopic studies allow us to obtain in-situ and quasi real-time electronic solid state spectra of two prototypical PAHs (pyrene and coronene) embedded in water ice under VUV photoprocessing. The study is carried out on PAH:H 2 O concentrations in the range of 1:30 000 to pure PAH, covering the temperature range from 12 to 125 K. Results. PAH concentration strongly influences the efficiency of PAH cation formation. At low concentrations, ionization efficiencies are over 60% dropping to about 15% at 1:1000. Increasing the PAH concentration reveals spectral broadening in neutral and cation PAH spectra attributed to PAH clustering inside the ice. At the PAH concentrations expected for interstellar ices, some 10 to 20% may be present as cations. The presence of PAHs in neutral and ion form will add distinctive absorption bands to cosmic ice optical spectra and this may serve as a tool to determine PAH concentrations.

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Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)

Cited by 17 publications

References 26 publications

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Amorphous Solid Water (ASW): Pulsed Laser Ablation of ASW/CO₂ Thin Films

Photochemistry of PAHs in cosmic water ice

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Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)

Cited by 17 publications

References 26 publications

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Cyclic cluster study of water adsorption structures on the MgO(100) surface

Amorphous Solid Water (ASW): Pulsed Laser Ablation of ASW/CO2 Thin Films

Photochemistry of PAHs in cosmic water ice

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Amorphous Solid Water (ASW): Pulsed Laser Ablation of ASW/CO₂ Thin Films