storage ring measurements of the dissociative recombination of h 3 + : a closer look holger kreckel...

Storage ring measurements of the dissociative recombination of H3

+: a closer look

Holger Kreckel University of Illinois at Urbana-Champaign

Kyle N. CrabtreeBrian A. TomBenjamin J. McCall

Oldřich Novotny*Annemieke PetrignaniMax H. BergDennis BingManfred GrieserClaude KrantzMichael Lestinsky*Mario B. MendesChristian NordhornRoland RepnowJulia StützelAndreas Wolf

TSRGroup

Universityof Illinois

Richard Thomas

StockholmUniversity

Henrik Buhr

WeizmannInstitute

*Columbia University, NY

DR 2010, Lake Tahoe, Aug19th 2010Holger Kreckel Storage ring measurements … of H3

+: a closer look

H He

C N O Ne

Mg

Fe

Si S Ar

The relevance of H3+:

astronomer‘s periodic table


+: a closer look

The relevance of H3+:

engine of interstellar chemistry

H3+ formation

H2 + c.r. H2++ e-

H2+ + H2 H3

+ + H

Proton-hop reactions

H3+ + X XH+ +H2

H 2

H 2+

C H 3+

C H 5+

C H 4

C H2 3+

C H2 2

C H3+

C H3 3+

C Hm n

C H+

C H 2+

N H2

+

H C O+

O H+

H O2+

H O3

+H O2

O H

C H C N H2 5

+

C H C N H3

+

C H N H3 2

+

H C N2

+

H C N

C H N H3 2

C H N H2

C H C N3

C H C N2 5

C H

C H C O3

+

C H O H3 2

+

C H C O2

C H O H3

H C OC H O H

C H O C H

2

2 5

3 3

C H2 5

+C H2 4

H C O2 3

+C O3

C H2

H C N3 3

+H C N3

H C N5

H C N7

H C N9

H C N11

C H3

C 4

+

C H4+

C H4 2+

C H4 3+

C H4

C H3 2

cosm ic ray

H 2N 2

C OO

H 2

H 2

e

e

e

ee

e

e

N

N H 3

H C N

C H C N3

e

C O

H O2

C H O H , e3

C

H 2

H 2

H 2

e

e

C H 3

+e

e eH C N

C+

e

C+

H 2

e eC

+

H 2H 2

e

C O

C

H

+

e

e


+: a closer look

Steady State: [H3+]

=

ke[e-][H2]

The enigma of H3+ in diffuse clouds

Cosmic ray ionization rate

DR rate coefficient


+: a closer look

10-7

10-8

10-10

10-9

10-11

year1970 1990 20001980 2010

“Perceived” H3+ DR rate coefficient

Glosik et al.(2000-2009)Stat. & flow. afterglow

Adams, Smith,Alge(1984)Flow. afterglow

Adams, Smith (1987)Flow. afterglow

Amano (1988)IR spectroscopy

Larsson et al. (1993)Storage ring McCall et al. (2003)

Storage ring

Kreckel et al. (2005)

Storage ring

Leu, Biondi,Johnsen (1973)Stat. afterglow

H3+

DR

rat

e co

effic

ient

at

300K


+: a closer look

Storage ring measurements: concept

• radiative relaxation of internal excitations (rotation, vibration)

• direct measurement

• 100% detection efficiency

• high resolution

Advantages

Problem

H3+ !

• radiative relaxation incomplete


+: a closer look

(1,00) theory

(2,00)theory

experimental data (T < 1ms)

experimental data (T > 2s)

(0,00) theory

Coulomb explosion results H3+

Kreckel et al., PRA 66, 052509 (2002)

Vibrations decay withinthe first 2s of storage

Some rotational statesstay forever


+: a closer look

H2Gas inlet

2 atm

Solenoid valve

-900 Vring

electrode

Pinhole flange/ground

electrode

H3+

“Cold” ion sources

Supersonicexpansion

CRYRING 2002

5 cm

Cryogenic ion trap

TSR2004


+: a closer look

● TSR electron temp. kT┴=0.5 meV ~ 6KkT||=25 μeV trap temp. 13 KKreckel, PRL 95, 263201 (2005)

● CRYRING kT┴= 2 meVion temp. 30-50 KMcCall, Nature 422, 500 (2003)

Storage ring results with “cold” H3+ ion sources

TheoryKokooulineand Greene


+: a closer look

+

orthoI = 3/2

paraI = 1/2

+

The holy grail: state specific measurements

H3+

rotationallevels


+: a closer look

Nuclear spin effect: exp. and theory 2005

۰para H2

۰normal H2

experimentkT┴=4 meV

theoryGreene et al.

- para- ortho

Kreckel et. al, PRL 95, 263201 (2005)


+: a closer look

Theory with more accurate resonance energies

S. Fonseca dos Santos et al., JCP 127, 124309 2007


+: a closer look

Quantifying nuclear spin effects

B. Tom et al., JCP 130, 031101 2009

Reducedrate coeff.


+: a closer look

skimmerdischarge electrode

pinhole

plunger

piezo actuator

locking nut

6 cm

high pressureH2 reservoir

low pressure

Piezo expansion source


+: a closer look

Cavity ring down measurements at UIUC

Difference frequency generation: 3.67 μm


+: a closer look

Transitions observed

HG


+: a closer look

Rotational temperature

pure H2 discharge, 2bar

Trot=110 K

1:5 H2:Argon discharge, 2bar

Trot=180 K

No vibrations found!


+: a closer look

Nuclear spin manipulation

1:5 n-H2 : Argon mixture p-H3+ fraction p3= (47.9 ± 2) %

1:5 p-H2 : Argon mixture p-H3+ fraction p3= (70.8 ± 2) %

ortho H3+ para H3

+ para H3+


+: a closer look

UI Champaign-Urbana

MPI-K Heidelberg

DR measurements at TSR

Test Storage Ring


+: a closer look

Absolute scale of the rate coefficient

electron beamswitched off

electron target lengthstorage ring circumference

electrondensity


+: a closer look

Comparison to CRYRING 2002

CRYRING 2002 (n-H2)

TSR 2009 (n-H2:Ar 1:5)

1 m


+: a closer look

H2+ + e-

beam vel.

Rotational temperature: imaging basics

d

2-dimensional imaging, point source

P(D)3-dimensional imaging, point source

d ~ √Ek

2-dimensional imaging, extended source

δtdetector


+: a closer look

2-dimensional imaging of the 3-body breakup

H3+ + e- H + H + H

ne(cooler) = 1.4 x 107 cm-3

ne(target) = 1.34 x 106 cm-3

expectedKER = 4.79 eV


+: a closer look

2-dimensional imaging of the 3-body breakup

950 K450 K200 K

rotational temperatures(uncertainties ~ 200 K)

H3+ + e- H + H + H


+: a closer look

Piezo source extraction potentials


+: a closer look

Conditions on-axis downstream of the nozzle

Collisional heating during Ion extraction?

skimmer


+: a closer look

Detailed comparison of the (reduced) rate coefficient

TSR / 22-pole trap 2007

CRYRING / Solenoid 2002

TSR / piezo 2009


+: a closer look

Nuclear spin dependence of the rate coefficient

1:5 n-H2 : Argon mixture

1:5 p-H2 : Argon mixture

p3= (47.9 ± 2) %p3= (70.8 ± 2) %

Extrapolation:100% ortho H3

+

100% para H3+

Reducedrate coeff.


+: a closer look

Summary• While we measure a rotational temperature of 200K with CRD spectroscopy,the stored H3

+ ions are much hotter than the ion source.

• We observed clear differences between different ion sources→ the heating is probably happening prior to injection into the ring .

• We observed for the first time detailed structures in the rate coefficients for ortho-H3

+ and para-H3+ at low energies.

The holy grail?

Still out there …

Results: Kreckel et al., submitted to PRAPetrignani et al., in preparation


+: a closer look

Perspectives:the case to continue the quest

Kyle N. Crabtree et al., to be published

It is crucial to understand:H3

+ + H2 andH3

+ (J=1,K=0,1) + e-


+: a closer look

Collaboration

Kyle N. CrabtreeBrian A. TomBenjamin J. McCall

Oldřich Novotny*Annemieke PetrignaniMax H. BergDennis BingManfred GrieserClaude KrantzMichael Lestinsky*Mario B. MendesChristian NordhornRoland RepnowJulia StützelAndreas Wolf

TSRGroup

Universityof Illinois

Richard Thomas

StockholmUniversity

Henrik Buhr

WeizmannInstitute

*Columbia University, NY

Funding: NationalScienceFoundation

Max-PlanckSociety

German-IsraeliFoundation

Eurppean Comission


+: a closer look

storage ring measurements of the dissociative recombination of h 3 + : a closer look holger kreckel...

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