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T Fuhrmann

Publications and source records attributed to T Fuhrmann.

9 recordsLinked to original sources
PubMed2006

A detailed analysis of vibrational excitations in x-ray photoelectron spectra of adsorbed small hydrocarbons.

The vibrational fine structure of x-ray photoelectron (XP) spectra of a number of different small hydrocarbon molecules and reaction intermediates adsorbed on Pt(111) and Ni(111) has been investigated in detail. The data for methyl, methylidyne, acetylene, and ethylene can consistently be analyzed within the linear coupling model. The S factor, i.e., the intensity ratio of the first vibrationally excited to the adiabatic transition, is obtained to be 0.17+/-0.02 per C-H bond; for the deuterated species a value of 0.23+/-0.02 is obtained. Therefore, the vibrational fine structure can be used for fingerprinting in the analysis of XP spectra and for identifying unknown reaction intermediates. From the data, Deltar, the change of the minimum in the potential energy curve upon core ionization, is calculated within the linear coupling model using a first order correction. For all adsorbates, including the deuterated ones, a value of Deltar=0.060+/-0.004 A is obtained. Furthermore, from the binding energy of the adiabatic peak and from the energy of the vibrational excitation in the ionic final state some information on the adsorbate/substrate bond and the adsorption site can be derived.

Journal Article↗
PubMed2006

A site-selective in situ study of CO adsorption and desorption on Pt(355).

Using time-dependent high-resolution x-ray photoelectron spectroscopy at BESSY II, the adsorption and desorption processes of CO on stepped Pt(355) = Pt[5(111) x (111)] were investigated. From a quantitative analysis of C 1s data, the distribution of CO on the various adsorption sites can be determined continuously during adsorption and desorption. These unique data show that the terrace sites are only occupied when the step sites are almost saturated, even at temperatures as low as 130 K. The coverage-dependent occupation of on-top and bridge adsorption sites on the (111) terraces of Pt(355) is found to differ from that on Pt(111), which is attributed to the finite width of the terraces and changes in adsorbate-adsorbate interactions. In particular, no long-range order of the adsorbate layer could be observed by low-energy electron diffraction. Further details are derived from sticking coefficient measurements using the method devised by King and Wells [Proc. R. Soc. London, Ser. A 339, 245 (1974)] and temperature-programmed desorption. The CO saturation coverage is found to be slightly smaller on the stepped surface as compared to that on Pt(111). The initial sticking coefficient has the same high value of 0.91 for both surfaces.

Journal Article↗
PubMed2004

Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopy.

High-resolution x-ray photoelectron spectroscopy has been used to study the kinetics of the CO oxidation reaction on a Pt(111) surface in situ. The study focuses on the interaction of a preadsorbed p(2x2) layer of atomic oxygen with CO dosed using a supersonic molecular beam. Measurements of O 1s and C 1s spectra at 120 K show that CO adsorbs on the oxygen precovered substrate, but no reaction occurs. A maximum CO coverage of 0.23 ML (monolayer) is observed, with CO exclusively bound on on-top sites. In accordance with the literature, bridge sites are blocked by the presence of atomic oxygen. The reaction of CO with preadsorbed O to CO(2) is studied isothermally in a temperature range between 275 and 305 K. The reaction rate initially increases with CO pressure, but saturates at 9x10(-7) mbar. The data indicate that a certain amount of disordered oxygen within the p(2x2) layer acts as a starting point of the reaction and for a given temperature reacts with a higher rate than O in the well-ordered oxygen p(2x2) phase. For the reaction of CO with this ordered phase, the results confirm the assumption of a reaction mechanism, which is restricted to the edges of compact oxygen islands. The activation energy of the reaction is determined to (0.53+/-0.04) eV, with a prefactor of 4.7x10(6+/-0.7) s(-1).

Journal Article↗
PubMed1991

[Social psychological barriers to compliance in group and individual prophylaxis].

In a long-term study of 700 school children attitudes and behaviour related to dental hygiene were registered and collated with findings on caries and oral hygiene. The data indicating developments in the 12 - 14 year old group showed that youths are well informed about the condition of their teeth, but are increasingly unwilling to accept treatment and advice offered by dentists. Potential barriers to compliance with prophylactic and therapeutic measures are a lack of success in school studies, insufficient accentuation of independence in the educational and child-raising process and a lack of communication between dentist and youths.

Adolescent↗
PubMed1990

[Studies on juveniles' education for health of teeth and mouth. 2. Juveniles' knowledge of dental health and behavior].

General recommendations about healthy way of life and dental health are well-known to juveniles aged 12 to 16; but detailed information which completes and reinforces this general knowledge in a useful way is to a large extent lacking. Knowledge and behaviour of juveniles correlate with age, sex and success at school. An important role in developing a healthy way of life plays the family education. Point of contact for the dentist is the upgrading of dental screenings by a conform-intensive arrangement of these direct and very individual consultations.

Adolescent↗
PubMed1989

[Juveniles' education for oral health. 1. Juveniles' position to health of teeth and stomatological care in children].

About one forth each of juveniles aged between 12 and 16 years which have been questioned in a written form to the topic of health declare a particular positive attitude towards a healthy way of live or a negative attitude towards dental health. The compliance of juveniles to dental care is influenced both by sex, age, achievements at school, family, group integration and their motivation structure and by paedodontics care.

Adolescent↗