Observation of single collisionally cooled trapped ions in a buffer gas

Individual Ba ions are trapped in a gas-filled linear ion trap and observed with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage times of ~5 min (~1 min) are achieved using He (Ar) as a buffer gas at pressures in the range 8e-5 - 4e-3 torr. Trap dynamics in buffer gases are experimentally studied in the simple case of single ions. In particular, the cooling effects of light gases such as He and Ar and the destabilizing properties of heavier gases such as Xe are studied. A simple model is offered to explain the observed phenomenology.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. A. Minor text and figure change

L'influence des parois en verre sur l'établissement des stratifications de la colonne positive

Dans le présent travail sont exposées certaines modifications d'aspect des phénomènes lumineux présentés par une ampoule à décharge (âir pression 0,08-1 mm Hg) dans des conditions définies. L'introduction d'un tube en verre étroit sur le trajet des particules a une influence déterminée sur l'établissement de la colonne anodique (apparition progressive des stratifications positives), tandis que les phénomènes lumineux catholiques ne sont pas influencés. La distribution du potentiel électrique le long des stratifications (décharge avec tube) a été explorée avec une sonde; les résultats sont concordants avec ceux prévus par K T. Compton, Turner et Mac Curdy. Les variations du potentiel électrique dans les régions de la décharge anodique, provoquées de la manière indiquée, sont également étudiées

Transistor por efeito de campo e fotocondutor de poli(o-metoxianilina).

RESUMO: Esse artigo apresenta resultados sobre fabricação e caracterização de um transistor por efeito de campo (FET) tendo a poli(o-metoxianilina) - POMA - como material ativo. Uma adaptação de processos de microeletrônica tradicional foi feita para a confecção desse dispositivo. O FET desenvolvido apresentou modulação por voltagem de porta Vg, mas operou mesmo em Vg=0. A corrente de dreno I D aumentou significativamente sob iluminação na região da radiação visível e infravermelho próximo, mostrando o caráter fotocondutor da POMA dopada e, portanto, do dispositivo. Um modelo teórico baseado nos mecanismos de condução eletrônica da POMA, e de efeitos de interface metal-polímero foi elaborado, ajustando-se muito bem aos resultados experimentais.<br>ABSTRACT: A field effect transistor - FET made from poly(o-methoxyaniline) (POMA), which is a conductive polymer, was developed. Several modifications were carried out to adapt the procedures generally used in traditional device developments. The characteristic of the FET produced was sensible to the gate modulation, but it operates even for V G = 0. The drain current I D enhanced under visible and near infrared radiation, showing the photoconductor character of POMA and, consequently, of the device. A theoretical model, based on the electronic properties of POMA and on the metal-polymer interface, was developed which is in good agreement with the experimental results