An STM

Measures I(r)

Tunneling is one of the simplest

quantum mechanical

process

A Laser STM for Molecules

Tunneling has transformed surface science.

Scanning the field around the molecule is like scanning the tip across a surface -- a molecular STM

H2 ionization in circularly polarized light

e

p

•The electron direction determines the field direction at the moment of ionization

•The bond softened ion determines the molecule’s direction at the moment of ionization

COLTRIMS – measuring the 3d-momenta of correlated particles

PRL 102, 033004 (2009)

The angle-dependent ionization probability

Implications of high tunneling rates:

)(

2/3

32

exp)(

2/5

04)(

tEaE

hEiE

tEaE

hEiEt

“DC” tunneling – The exponent is ~ 30-40. A small change in Ei is highly leveraged by the large Ea/E(t).

Laser tunneling: -- The exponent is ~ 8. The leverage is weakened. Lower orbitals will contribute.

PRL 94, 033003 (2005)

Measuring excited states

The laser STM senses the structure of orbitals: SU1 – direct tunneling

SU2 – excitation by bound state interaction with the departing electron

IP~4 eV

Applying the “laser STM” to HCl

Deeper orbitals tunnel ionize (directly)

HCl

Two or more orbitals can ionize

Transient alignment of molecules

time

Phys. Rev. A. 68, 023406 (2003)

2

exp)(2

E

IPppc

A molecular STM has much more information

Normalized Differences

Notice:

1 Low lateral momentum structures – tunneling

and

2 High lateral momentum structures – elastic scattering

Science 3201478 (2008)

pmolecule

pnormal

laser

The Model:1. Assume

2. Propagate swarm of electron trajectories classically

3. Including electron-ion interaction

4. Include alignment distribution

2

exp)(2

E

IPppc

Low Lateral momentum electrons

Science 3201478 (2008)

N2 O2 CO2

PRL 98, 243001 (2007)

The angle dependent probability

Transparent Solids: E = O(10eV)

a b c

-SiO2 Al2O3 LiF

crystal structure

Extending to Solids? The Lawn Mower Model

Tim e

R adius

• Self-controlled energy deposition.

• electron and energy density is predicted.

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

0 50 100 150 200 250 300

Input Pulse Energy (nJ)

No

rmal

ized

Tra

nsm

issi

on

Opt. Express 13, 3208 (2005).

G

K

M

SiO

Transmission as a function of angle

Angle dependent changes in the reduced-mass change the ionization rate.

(/2)

0

2.5

5

Quartz

0

0.5

1

Sapphire

0

2.5

5

LiF

0.5 1 1.5 2 2.5 3 3.5 4 4.50

0.5

1

azymuthal symmetry in transmission [ x - fold ]

Fused Silica

0

2.5

5

Quartz

0

0.5

1

Sapphire

0

2.5

5

LiF

0.5 1 1.5 2 2.5 3 3.5 4 4.50

0.5

1

azymuthal symmetry in transmission [ x - fold ]

Fused Silica

~ m3 resolution

crystallinefused

Only the focal region is measured

Phys. Rev. Lett. 101, 243001 (2008)

0

amorphous

crystal

The laser STMAtoms: The filter function

• using circular polarization.

Molecules: The orbital

• Filtered image of the orbital

• Quantify the contribution of lower orbitals.

Solids: The reduced tunneling mass

• Measuring crystal symmerty

Link to HHG – correlated measurements

• A mixture of optical and collision science

•Coherence can be transferred several times between electrons and photons

•The mixture offers new opportunities for each

To optics -- Angstrom spatial imaging.

To collision physics -- Time resolution.

Bertrand P1, Wörner P3, Meckel

Three new forms of nonlinear spectroscopy

1 Tunneling (to characterize orbitals)

2 Elastic scattering or Laser Induced Electron Diffraction (to determine nuclear positions) – see Meckel et al.

3 Interferometry (to image orbitals --photoelectron spectroscopy in reverse) – see poster by Bertrand P1 and Wörner P3

The tunneling electron wave packet of O2