Pore interconnectivity of nanoclustering silica porous films as studied by positronium time-of-flight spectroscopy

Ito, Kenji; Yu, Ruan; Sato, K.; Hirata, Koichi; Kobayashi, Yoshinori; Kurihara, Toshikazu; Egami, Miki; Arao, Hiroki; Nakashima, Akira; Komatsu, Michio

doi:10.1063/1.2125121

Cited by 29 publications

(28 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The value of ξ estimated with the MC is 1.7. This is consistent with the expectation of the analytical result and the values reported in previous experiments [30,32,33,38,40].…”

Section: B Tof Measurementssupporting

confidence: 93%

See 1 more Smart Citation

Measurement of the orthopositronium confinement energy in mesoporous thin films

et al. 2010

View full text Add to dashboard Cite

In this paper, we present measurements of the ortho-positronium (ortho-Ps) emission energy in vacuum from mesoporous films using the time-of-flight technique. We show evidence of quantum mechanical confinement in the mesopores that defines the minimal energy of the emitted Ps. Two samples with different effective pore sizes, measured with positron annihilation lifetime spectroscopy, are compared for the data collected in the temperature range 50-400 K. The sample with smaller pore size exhibits a higher minimal energy (73 ± 5 meV), compared to the sample with bigger pores (48 ± 5 meV), due to the stronger confinement. The dependence of the emission energy with the temperature of the target is modeled as ortho-Ps being confined in rectangular boxes in thermodynamic equilibrium with the sample. We also measured that the yield of positronium emitted in vacuum is not affected by the temperature of the target.

show abstract

“…The value of ξ estimated with the MC is 1.7. This is consistent with the expectation of the analytical result and the values reported in previous experiments [30,32,33,38,40].…”

Section: B Tof Measurementssupporting

confidence: 93%

“…Recently, this technique was applied to study mesoporous and hybrid silica films [32][33][34][35][36][37], to evaluate the continuity barrier [38] and the effect of thermalization for pore surfaces decorated with different groups [39]. However, the influence of the temperature on Ps emission in vacuum from mesoporous thin films was never studied in detail.…”

mentioning

confidence: 99%

Measurement of the orthopositronium confinement energy in mesoporous thin films

et al. 2010

View full text Add to dashboard Cite

show abstract

“…Nagashima et al [64] have attributed peaks observed at 1 and 3 eV to bulk and surface emission, respectively. In fact, various emission energies have been observed, all in the range of 1-3 eV [65][66][67][68]. The exact value in a given sample may depend on surface chemistry or bulk impurities.…”

Section: B Ps Coolingmentioning

confidence: 99%

Positronium cooling in porous silica measured via Doppler spectroscopy

Crivelli²,

et al. 2010

View full text Add to dashboard Cite

We have measured the kinetic energy of positronium (Ps) atoms emitted into a vacuum from a porous silica film subsequent to positron bombardment, via the Doppler spread of the linewidth of the Ps 1 3 S-2 3 P transition. We find that the deeper in the target film that positrons are implanted the colder is the emitted Ps, an effect we attribute to cooling via collisions in the pores as the atoms diffuse back to the film surface. We observed a lower limit to the mean Ps kinetic energy associated with motion in the direction of the laser, E x = 42 ± 3 meV, that is consistent with conversion of the confinement energy of Ps in the 2.7-nm-diameter pores to kinetic energy in vacuum. An implication is that a porous sample would need to be composed of pores greater than around 10 nm in diameter in order to produce thermal Ps in vacuum with temperatures of less than 100 K. By performing Doppler spectroscopy on intense pulses of Ps we have experimentally demonstrated the production of many excited-state Ps atoms simultaneously, which could have numerous applications, including laser cooling and fundamental spectroscopic studies of Ps and the production of antihydrogen.

show abstract

“…At present PAS techniques have been mainly applied in study of low-k films for microelectronic industry [3][4][5][6]. To our knowledge only few PAS works have been done on membranes, see Ref.…”

Section: Introductionmentioning

confidence: 99%