Laser induced molecular motion in strong nonresonant laser fields

نویسنده

  • Simon Mark Purcell
چکیده

The optical dipole force from a singe focussed laser beam was used to study the role of laser-induced molecular alignment on the centre-of-mass motion of carbon disulphide molecules in a molecular beam. The translational, rotational and vibrational temperatures of the CS2 molecules were measured to be 3.4±0.2 K, 35±10 K and 250±14 K respectively. The velocity of the beam was measured to be 542±22 m s−1. Time-of-flight mass spectroscopy was used to measure the acceleration and deceleration of the molecules. Maximum velocity changes of 7.5 m s−1 and 10 m s−1 were recorded for linearly and circularly polarised light respectively. These results showed that the dipole force, F ∝ ∇[αeff (I)I(r)], where αeff is the effective polarisability and determined through laser-induced alignment, can be modified by changing the laser polarisation. For linearly and circularly polarised light, a 12 % difference in effective polarisability was measured to produce a 20 % difference in dipole force. The dipole force from a single focussed laser beam produces a molecular optical lens and the downstream density of the molecular focus was probed by measuring the ion signal for both laser polarisations. The focal lengths for linearly and circularly polarised light were found to be separated by ≈100 μm. By altering the laser polarisation from linearly through elliptically to circularly polarised light, the focal length of the molecular optical lens could be smoothly altered over the ≈100 μm focal range. The role of the effective polarisability of each rotational state was also studied numerically. Separate rotational states were found to significantly alter the focal properties of a molecular optical lens. In CS2, higher rotational states (J > 10), exhibit less molecular alignment and when occupied, the focal length of the molecular optical lens for these states was increased by 60 % compared to the ground state.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Experimental Study of the Laser Induced Flow and Thermophoresis of Suspending Microparticles

The induced flow effect is the rotary motion generated in the fluid flow due to the temperature gradient. The phenomenon of thermophoresis is the movement of particles from the warmer side of the fluid to the cooler side. Laser is a very suitable device for creating a temperature gradient due to its unique features such as high power density, harmonic waves, single wavelength and very low diver...

متن کامل

Laser safety importance in clinical laser applications

Introduction: By introducing of laser systems and their continuous development, a new chapter of laser systems applications in a variety fields including research and clinical science in addition to the therapeutic, diagnostic applications were available for medical professionals in various fields. Most lasers emit radiation with intrinsic probable risks where in laser-tissue i...

متن کامل

Efficient nonresonant dipole force on molecules by a tightly focused laser

*Correspondence: Doo Soo Chung, Molecule Optics and Bioanalytical Chemistry Lab, Department of Chemistry, Seoul National University, Seoul 151-747, South Korea e-mail: [email protected]; Bum Suk Zhao, Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology, 50 UNIST-gil, Bldg. 103, Ulsan 689-798, South Korea e-mail: [email protected] When a molecule...

متن کامل

Propagation and Interaction of Electrostatic and Electromagnetic Waves in Two Stream Free Electron Laser in the Presence of Self-Fields

A relativistic theory for two-stream free electron laser (FEL) with a one-dimensional helical wiggler and ion-channel guiding in the presence of self-fields are presented. A dispersion relation (DR) which includes coupling between the electromagnetic and the electrostatic waves is derived from a fluid model, with all of the relativistic terms related to the transverse wiggler motion. This DR is...

متن کامل

Field-free three dimensional molecular axis alignment.

We investigate strategies for field-free three dimensional molecular axis alignment using strong nonresonant laser fields under experimentally realistic conditions. Using the polarizabilites and rotational constants of an asymmetric top rotor molecule (ethene, C2H4), we consider three different methods for axis alignment of a Boltzmann distribution of rotors at 4 K. Specifically, we compare the...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2010