Excimer

About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.

A study on mechanism of excimer formation through fluorescence quenching for isotactic and atactic polystyrenes and poly(p‐methylstyrenes) in solution

Abstract: The mechanism of excimer formation and deactivation for isotactic and atactic polystyrenes, and isotactic and atactic poly(p-methylstyrenes) was studied by comparison of the rate parameters which were calculated from the fluorescence quenching and the decay time measurements of excimer emission band. The activation energy of excimer formation was obtained from the effect of temperature change on fluorescence intensity. The rate parameters of excimer formation for isotactic polymers are in the order of 109 s−1 and larger than those for atactic polymers. The activation energy for isotactic polymers is smaller than that for atactic polymers. These results show that isotactic polymers can form the excimer more easily than atactic polymers. The facility of excimer formation for isotactic polymers is interpreted as lower energy barrier required to achieve the excited excimer state.

Laser-induced fluorescence studies of the CH3S radical

Abstract: Methylthio radicals (CH3S) have been generated by the 248 nm photodissociation of dimethyl disulphide [(CH3S)2] and 193 nm photodissociation of methylmercaptan [CH3SH]. Fluorescence has been excited on the A2A1â†�X2E transition. The transitions excited were 320 at 366.0 nm, 310 at 371.3 nm and 000 at 377.0 nm. Vibrational relaxation and electronic quenching of the upper state have been studied with a number of gases. By varying the delay between the excimer and dye laser pulses, it has also been possible to study vibrational relaxation in the ground state in the presence of the same gases. No reaction of the CH3S radical could be found with either O2 or O3(kO3⩽ 8 × 10–14 cm3 molecule–1 s–1), although the fast reaction with NO2 was confirmed.

Titanium alloy surface modification by excimer laser irradiation

Abstract: The main effects of the interaction of UV emitting KrCl (at 222 nm) and XeCl (at 308 nm) excimer lasers with titanium alloy Ti6Al4V are presented. Single-pulse and multi-pulse irradiations were used, with varying laser beam fluences. The resulting interactions with the surface show thermal character, and produce: (i) damages in the form of craters at higher pulse counts and fluences of 7 J cm−2 and 7.2 J cm−2, which are far above the damage threshold; (ii) melt pools with visible wave-like structures at periphery; (iii) resolidified droplets and cracks at periphery (at higher pulse count), (iv) increasing content of oxygen, with a domination of TiO2.