Release Time:2019-03-09  Hits:

Indexed by: Journal Article

Date of Publication: 2013-11-01

Journal: EUROPEAN PHYSICAL JOURNAL D

Included Journals: Scopus、SCIE

Volume: 67

Issue: 11

ISSN: 1434-6060

Abstract: An efficient three-step excitation scheme is proposed to achieve the strong molecular orientation. By taking the CO molecule for example, via the Raman excitation by the femtosecond pulse L-1 and subsequently resonant excitations by a single-cycle THz pulse L-2, the high degree of the field-free orientation of vertical bar < cos theta >vertical bar(max) = 0.8921 can be obtained at the rotational temperature T = 0 K. An additional single-cycle THz pulse L-3 is introduced to further regulate the population distribution on rotational states and decrease the reduction of the orientation originating from the offset phase. With the increase of the central frequency omega(3) of L-3, the optimal vertical bar < cos theta >vertical bar(max) increases monotonically. When omega(3) - 1.0 THz, the degree of the field-free orientation reaches vertical bar < cos theta >vertical bar(max) - 0.9401. Moreover, our scheme is robust against the rotational temperature. Although the molecular orientation weakens with the rise of rotational temperature, vertical bar << cos theta >>vertical bar > 0.5 is still obtained until T = 22.8 K.