준안정적 헬륨원자의 23S1→33P2→263S1 연속단계에서 AC Stark 효과

정도영, 이강수, 최안성 +3 more

남백일, 강석찬, 김영순

남백일, 강석찬, 김영순

김중복, Thomas R. O’Brian, Thomas B. Lucatorto

Xe 원자의 14개의 Rydberg 준위들이 강한 레이저 광(6 GW/㎠ 정도까지) 아래서 ac Stark 효과에 의하여 이동하는 것을 약한 파장 가변 레이저를 이용하여 측정하였다. 시공간적으로 두개의 레이저광을 정확하게 일치시킴으로써 모든 준위들이 ponderomotive 값에 거의 일치하여 이동됨을 확인하였다. 강도가 큰 레이저 광을 원자에 조사킬 때 광의 강한 전기장에 의한 여기 준위의 AC Stark 이동이 high-frequency approximation (구속 에너지보다 매우 큰 광에너지에 의한 섭동 이론) 결과에 의하면 ponderomotive 이동이 예상되는데 본 연구를 통하여 그 일치를 확인하였다. 측정한 AC Stark 이동 값을 2광자 공명 3광자 이온화 모델에 사용함으로써 얻은 스펙트럼이 실험 결과와 잘 일치하였다.

Seunghyun LEE, Deuk Su KIM, Ki Tak WON +1 more

Jason R. Reeves

Resist based neutral atom lithography with metastable 23S1 helium(He. ) has been used to produce small structures in both goldand palladium. A beam of He. from a reverse flow, DC dischargesource is collimated by the bichromatic optical force followed bythree optical molasses velocity compression stages. The He. beamthen crosses a region where a mechanical or optical mask createsthe desired pattern.In the first experiments, a self assembled monolayer (SAM) ofnonanethiol is grown on a gold coated silicon wafer and then exposedto the bright, collimated beam of He. after a Nickel micromesh mask. The mesh protects parts of the SAM from the 20 eVof internal energy deposited by the impact of a He. atom onto thesample surface. The pattern of the mesh is transferred into the~200 Å gold layer with a standard selective etch that removes theGold from under the damaged SAM molecules. The samples wereanalyzed with an Atomic Force Microscope and Scanning ElectronMicroscope.The second set of experiments were performed using an opticalmask to pattern a gold coated silicon wafer. In the optical mask,the He. atoms experience the dipole force while traversing a standinglight wave of &lambda1<\sub> = 1083 nm light tuned 490 MHz above the 23S1<\sub>→ 23P2 transition or, in separate experiments, &lambda2<\sub> = 389 nmlight tuned 80 MHz below the 23S1<\sub>→ 33P2 transition. Using theoptical masks, He. can be focused or channeled into parallel linesseparated by &lambda/2 by varying the intensity of the standing lightwave.The small structures created by the 389 nm optical mask beganapproaching the gold surface granularity. A ~200 Å layer of palladium on silicon was chosen as the palladium granularity is muchsmaller and the SAM of nonanethiol will still form on the surface.Experiments using a nickel micro mesh as a mechanical mask havedemonstrated similar features to those in gold.