FAST-ION-BEAM ATOMIC SPECTROSCOPY

Toledo Heavy Ion Accelerator

(THIA)

Laboratory

PROPERTIES OF FREE ATOMS

A free atom can be characterized by its energy levels, oscillator strengths, population amplitudes, and g-factors. (The oscillator strengths are the spring constants that characterize its distortions)

1. Have discrete orbital energies (level structure) 2. Undergo radiative transitions (wavelengths)3. Transitions have natural linewidths (lifetimes)4. Decay has branched exit channels (intensities)5. Levels have population amplitudes (coherence)6. Orbitals have magnetic moments (g-factors)

PROPERTIES OF ATOMS IN ARBITRARYENVIRONMENTS (ALL KNOWN MATTER)

1. The same as those of the free atom, except the eigenstates are different.

2. Eigenstates of a free atom comprise a complete basis set.3. An atom in an arbitrary environment can be described as

a coherent superposition of amplitudes of the free atom, if its energy levels and spring constants are known.

(For example, electric polarizabilities, indices of refraction, virial coefficients, scattering cross sections, etc, are all sums of oscillator strengths multiplied by appropriate powers of energy factors.)

700 Li+ beam (v=4.4 mm/ns) incident on a thin (3 g/cm2) carbon foil. The blue light is H-like 4f-5g in Li2+ (4500Å, =3 ns, x=1.3 cm).

The green light is He-like 2s 3S-2p 3P in Li+ (5485Å, =44 ns, x=19 cm).

McMaster Hall Room 1019

slowest ions exiting foil < v < speed of lightshortest resolvable length < v < longest non-divergent path

Multiplexed Simultaneous PSD Efficient detection of a range of ’s Allowed & forbidden transitions are manifest Time-dep: beam fluctuations cancel in ratios; line profiles reveal blends; bkgds obtained between lines; ANDC possible in real time

2-E1 decay of 1s2s 1S0 in He-like Br - (bkgd: M1 decay of 1s2s 3S1 ) Spike: Random

M1+M1. Ridges: Random M1+Continuum Diagonal island: Real E1+E1

Differential Quantum Beat Measurements

SpectrometerRefocussing

Eliminateblending

ANDCMethod

EliminateCascading

Adjusted Normalization of Decay Curves

1951

King Gustav IV Adolf

Professor Bengt Edlén

ISOELECTRONIC SYSTEMATIZATION

Line Strength Factor:

Sif mi mf

i | r/ao | f 2

Deduced from measured data:

Sif = [ if(Å) / 1265.38]3 gi Bif / i(ns)

Parametrized:

Z2Sif SH + b/(Z-C) ; SH = 3n2 (n2-1) gi / 4

Cancellation

Singlet-Triplet Mixing

nsnp levels

INT

RES

MixingAngles

Alkaline-earthlike sequences

Ca II

Branching fractions:VIS, IR, UV, VUVcalibrations needed

Determination of branching fractions: Requires intensity calibration of detection apparatus as a function of wavelength

Standard lamps: continuum radiation fixed in laboratory beam light Doppler shifted

Line standards available in Visible, but not UV

Need in-beam ions with known intensity ratios

Si sequence

S II : (Å)907, 911, 9131053, 10561167, 1173

Differential Lifetime Measurements

MCDHF Calculations

8-1/2 =0.3535

5670