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The dissociation and ionization dynamics of CF3I and CH3I molecules were investigated using a pump-and-probe technique that employs a soft x-ray free-electron laser (SACLA) in Japan. First, time-resolved inner-shell photoelectron spectroscopy was employed to observe the ultrafast reaction of CF3I by monitoring iodine 4d electrons. The change in the I 4d state observed in the photoelectron spectra is found to occur with a rise time τ of approximately 40 fs after a pump laser pulse, which is faster than that observed when an ultrafast gas-phase electron diffraction technique is employed. This implies that the inner-shell photoelectron spectroscopy is more sensitive to the potential surface near the Franck–Condon region. Second, a strong laser intensity at 266 nm, corresponding to a power density of 1.9 × 1014 W cm−2, can easily ionize CH3I molecules via multiphoton ionization processes, and the time dependence of the valence photoelectron spectra clearly shows that at the picosecond timescale, this pump laser pulse causes spectral peaks to shift owing to space-charge effects in response to the large amount of ions generated. Thus, the SACLA can be a useful tool to investigate not only the dynamical process of molecular dissociation but also the ionization process through the shift in the peaks of photoelectron spectra. [ABSTRACT FROM AUTHOR]

The source of V1 layer of the Venus ionosphere is as enigmatic as its very existence itself. Discovered, for the first time by the radio occultation experiment (VeRA) onboard Venus Express, it is known to exist at about 125 km altitude and has been surmised to be caused by soft X-ray emissions [1]. A characteristic feature of this ionospheric layer as well as consensus on its source, however, is yet to emerge mostly because of the lack of observation opportunities. In this context, radio occultation measurements of the Venus ionosphere using Akatsuki measurements assume significance as these not only add to the data base but also give measurements from the low latitude regions which have remained less explored during previous missions due to satellite trajectory [2]. In this paper, we study the characteristics of V1 layer using some thirty radio occultation measurements done since 2016 both at UDSC in Japan, and IDSN in India [2]. Only those measurements were considered where the ionosphere was in the sunlit side and solar zenith angle was less than 85 degree. In all we got sixteen profiles satisfying these conditions. We get several profiles from the low latitude regions of the Venus ionosphere giving some interesting features of the V1 layer. Interestingly, distinct V1 layers were not visible in many cases. While in some profiles it appeared as a ledge, there were a few examples too when a very distinct peak was also visible. The origin for such features has been explored using an in-house developed one dimensional photochemical model for the Venusian ionosphere (1DPCM) [3]. Though both the peak V1 layer height and density get neatly reproduced in the model, in most of the cases we note the model V1 layer appears only as a shoulder. A detailed comparison of the model and Akatsuki derived altitude profiles of the Venus ionosphere under varying solar conditions would be provided and reasons for the occurrence of V1 layers of varying characteristics would be discussed. [ABSTRACT FROM AUTHOR]

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