Research On Branching Fractions Of The 4P_3/2 State And Characteristics Of The Magic Wavelength In ⁴⁰Ca⁺

Precision measurement physics can discover new physical phenomena by improving measurement precision.With the development of science and technology,more and more methods are adopted for measuring physical quantities and the precision increases rapidly.Ions can be constrained by ion traps for a long time and can be cooled to mK or even ?K by laser cooling.Meanwhile,the ion traps are placed in ultra-high vacuum environment(UHV),which leads to small collision probabilities between ions and background gases.So,trapped ions are widely used in precision measurement field and optical frequency standards.Because of the simple energy level structure of 40Ca+,all radiations needed for the study can be generated by diode lasers,which brings great development of precision measurement on 40Ca+.In this thesis,the author summarize the works on precision measurement of two physical parameters in 40Ca+,one is the measurement of branching fractions of the 4P3/2 state,another is the study of the relationship between optical frequency shift of clock transitions and laser polarization direction.Precision measurement of the branching fractions is favorable to the determination of relevant transition matrix element,can test the accuracy of the theoretical model which can then promote the development of relativistic multi-body theory,What's more,the precison values of both lifetimes of the metastable states and the branching fractions can improve the accuracy of relevant states' static polarizabilities of the clock transitons in 40Ca+ which can reduce the error from black body radiation in clock standard.Ac-Stark effect is quite an important systematic error source.So,sduty on the characteristics of ac-Stark shift is favorable to seek a proper method to reduce the error from ac-Stark effect.This thesis describes the relevant work in detail,the main content is categorized as follows:1.The experimental platform is established.It mainly consists of an ultra-high vacuum system,a linear ion trap system,the laser system and fluorescence detection system.Meanwhile,magnetic field control is also accomplished.2.The branching fractions of the 4P3/2 state in 40Ca+ are measured.The lasers are switched precisely by use of time sequence.By counting the photons scattered from ions in different steps with hundreds of ions trapped in the linear Paul trap,the branching fractions are deduced to be 0.9350(4),0.0587(4),and 0.0063(2),respectively,which agree with the recent experiment and theoretical values.3.The relationship between frequency shift of clock transitions(4S1/2,m=±1/2?3D5/2,m±1/2)and laser polarization direction in 40Ca+ are studied.By measuring the optical shifts with different polarization angles of the light,we found the shifts change periodically with the polarization angle of the light.