title: Damped and thermal motion of laser-aligned hydrated macromolecule beams for diffraction.
abstract: We consider a monodispersed Rayleigh droplet beam of water droplets doped with proteins. An intense infrared laser is used to align these droplets. The arrangement has been proposed for electron- and x-ray-diffraction studies of proteins which are difficult to crystallize. This paper considers the effect of thermal fluctuations on the angular spread of alignment in thermal equilibrium, and relaxation phenomena, particularly the damping of oscillations excited as the molecules enter the field. The possibility of adiabatic alignment is also considered. We find that damping times in a high-pressure gas cell as used in x-ray-diffraction experiments are short compared with the time taken for molecules to traverse the beam and that a suitably shaped field might be used for electron-diffraction experiments in vacuum to provide adiabatic alignment, thus obviating the need for a damping gas cell.
authors.affiliation: Department of Physics and Astronomy, Arizona State University, P.O. Box 871504 Tempe, Arizona 85287-1504, USA. dmitri.starodub@asu.edu
authors.forename: D
authors.initials: D
authors.lastname: Starodub
authors.forename: R B
authors.initials: RB
authors.lastname: Doak
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.forename: U
authors.initials: U
authors.lastname: Weierstall
authors.forename: J S
authors.initials: JS
authors.lastname: Wu
authors.forename: J C H
authors.initials: JC
authors.lastname: Spence
authors.forename: M
authors.initials: M
authors.lastname: Howells
authors.forename: M
authors.initials: M
authors.lastname: Marcus
authors.forename: D
authors.initials: D
authors.lastname: Shapiro
authors.forename: A
authors.initials: A
authors.lastname: Barty
authors.forename: H N
authors.initials: HN
authors.lastname: Chapman
mesh_terms: D002627:Chemistry, Physical / Q000379:methods; D003460:Crystallization; D004583:Electrons; D005740:Gases; D007834:Lasers; D046911:Macromolecular Substances; D015233:Models, Statistical; D009113:Muramidase / Q000737:chemistry; D009991:Oscillometry; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D005740:Gases; D046911:Macromolecular Substances; D011506:Proteins; D009113:Muramidase