Enhancement of the bimolecular reaction of hydrogen iodide by vibrational excitation

✍ Scribed by Hiroyuki Horiguchi; Soji Tsuchiya

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 719 KB
• Volume: 13
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550131008

✦ Synopsis

The himolecular reaction of HI in CO2, which was excited vibrationally by irradiation of a continuous-wave CO2 laser light, was investigated in the temperature range of 721-980 K. An enhancement of the reaction rate by a factor of about 2.5 was observed in the 1:l HI-CO2 mixture in comparison with the rate in pure HI when both sample gases were irradiated by a CO2 laser (50 W) a t 1 torr. However, in the HI-SFe mixtures the decomposition rate of HI was not accelerated by irradiation of the C02 laser. Thus the enhancement is attributed to vibrational excitation of HI through collisional energy transfers from laser-excited CO2 (OOol).

At lower total pressures or a t lower partial pressures of HI in HILC02 mixtures the enhancement was more significant because of inefficient vibrational deactivation of excited HI. A model calculation gave the result in agreement with the experimental one if the effective activation energy is assumed as EA = E, -(~E,ib, where E, is the activation energy for the thermal reaction, E v i b is the vibrational energy of two colliding HI molecules, and (Y is estimated to he ahout 0.7. This means that a part of the vibrational energy of reacting HI is employed to reduce the activation energy for the translational or rotational degree of freedom.