検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

A Role of rotational energy transfer in H$$_{2}$$ ortho-para conversion

H$$_{2}$$オルト-パラ転換における回転エネルギー移動

植田 寛和   ; 福谷 克之

Ueta, Hirokazu; Fukutani, Katsuyuki

H$$_{2}$$ has two nuclear spin isomers, ortho-H$$_{2}$$ (o-H$$_{2}$$) and para-H$$_{2}$$ (p-H$$_{2}$$). Due to symmetry restriction, o-H$$_{2}$$ and p-H$$_{2}$$ with parallel and antiparallel proton spins have odd and even rotational states, respectively. Interconversion between these two species, ortho-to-para (o-p) conversion is of great interest not only from a fundamental point of view but also in industrial applications such as H$$_{2}$$ liquification and storage. While the radiative o-p conversion is forbidden in the gas phase, the conversion is promoted on various surfaces. The o-p conversion is completed by the nuclear spin flip and the rotational energy transfer. The former process has been paid much attention in previous o-p conversion studies, but the detail of the latter one remains unclear. In this contribution, we deal with the o-p conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210). This system allows us to probe the o-p conversion at a wider range of surface temperature as compared with physisorption systems. A combination of a pulsed molecular beam, photo-stimulated desorption and resonance-enhanced multiphoton ionization techniques is used to probe time evolution of o-H$$_{2}$$ and p-H$$_{2}$$ populations. Figure 1 shows that o-p conversion occurs with a conversion time of about 2 sec at a surface temperature of 50 K. To obtain insight into a role of rotational energy transfer in o-p conversion, we further study the surface temperature dependence of o-p conversion and the reverse process of p-o back conversion. From the results obtained the conversion mechanism will be discussed.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.