8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.88Wed 711:10-14:00Roles of gas molecules on electrospray phenomenonHitomi Kobara, 1 Akihiro Wakisaka, 1 Masahiro Tsuchiya, 2 Atsushi Ogata, 1 Hyun-haKim, 1 and Kazuo Matsuura 31 National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa,305-8569, Tsukuba, Ibaraki, Japan2 National Defense Academy of Japan, Yokosuka, Kanagawa, Japan3 Nanomist Technologies Co. , Ltd. , Naruto, Tokushima, JapanElectrospray is widely used in the field of industry, but its mechanism has not been completelycleared. When the electrospray of ethanol was carried out under N 2 atmosphere, liquid is hardlyatomized with increasing voltages. However, the electrospray was maintained stably under a ratioof N 2 /O 2 = 4/1 atmosphere. This difference was remarkable when the negative voltage wassupplied. Here we report the effect of atmospheric gas molecules on the electrospray phenomenon.Under N 2 atmosphere, with increasing the electric potential of the nozzle to the large negativevalue, light emission was increased around the nozzle, while the generation of the liquid dropletswas suppressed remarkably. This emission spectrum was identified to be N 2 (C-B) transitions.The increase in the intensity of the emission for N 2 (C-B) was synchronized with the decreasein the electrospray efficiency. Such simultaneous observations can be explained as follows: 1)N 2 + ions are generated by collisions of N 2 molecules with high-energy electrons emitted fromthe nozzle at the highly negative potential, 2) N 2 + ions are accelerated toward the nozzle dueto the electric potential, and are recombined with high-energy electrons to form excited-state N 2molecules, which results in the light emission, and 3) When the electron transfer from the nozzleto the N 2 + becomes predominant, the electrospray is suppressed. In the presence of O 2 molecules,electrons are trapped by O 2 molecules because of their large electron affinities. This protects theelectron impact to N 2 molecules to decrease the emission, and leads to the stable electrospray evenat large negative potentials. Our results demonstrate that the atmospheric gaseous molecules playthe important roles in the electrospray.88