QM drives "astro-chemistry" ?

[Widdekind]

In star-forming clouds, grains of 'dust' are:

 

bits of soot & silicates [i.e., C & Si] that can develop mantles of ice, several layers thick. The ice itself is usually frozen water; but, other componds such as ammonia, methane, & carbon dioxide, may also be present. When temperatures inside a cloud plumet, gases can condense onto grains the way that ice builds up inside a freezer (Science News 2010)

However, cold solid ices are normally chemically inert. So, to explain astro-chemical reactions, between spatially separated species of grain-bound, ice-locked astro-chemicals, researches have hypothesized, that:

 

Cosmic Rays or UV photons [might] penetrate these icy bits of dust, spurring reactions, even in ice [by] creating tunnels, through which electrons can travel, to meet species locked in the ice. (Or, gas-phase species can land on an ice grain, and connect with molecules bound to ghe grain's surface) (ibid.).

In the cold, rarified conditions, of star-forming clouds, could quasi-isolated dust grains -- "in space, the time between collisions can be weeks to years" (ibid.) -- be quantum mechanically "isolated", so that quantum phenomena, e.g. 'tunneling', might play important roles, in astro-chemical reactions ??

[John Cuthber]

QM drives all chemistry.

[mississippichem]

We already know of many photochemical reactions.

 

And yes, QM does "drive" ALL chemistry.

[Widdekind]

What about 'exotic' QM phenomena, e.g. 'tunneling' ?

[mississippichem]

What about 'exotic' QM phenomena, e.g. 'tunneling' ?

 

Definitely. People are now beginning to learn that many reactions are dominated by tunneling phenomena. This includes fast proton transport systems in biological systems, and many ordinary organic chemistry reactions that display kinetics faster than diffusion should allow.

 

I wouldn't really even call tunneling an exotic phenomenon because its really just an elementary consequence of QM. There's already technology based on tunneling like scanning tunneling microscopy and atomic force microscopy.

 

Though I do find it fascinating.

Edited November 23, 2011 by mississippichem

[imatfaal]

Mississippichem or JC can correct me - but far from quantum tunnelling being an exotic and rare phenomenon I believe that the rate of fusion within the Sun is highly dependent on quantum tunnelling; the temperature of the Sun is too low for a self-sustained fusion - but two factors mean that fusion does occur at a sustaining rate, that many particles have higher than the average temperature and that quantum tunnelling allows the important reactions sometimes to take place at a lower energy than expected

[Widdekind]

Can I call Imatfaal correct ? According to Mazure's Exploding Superstars, the tunneling probability

 

[math]P_T \propto e^{-\left(\frac{E_G}{E}\right)^{1/2}}[/math]

where [math]E_G \equiv 2 m c^2 \left(\alpha \pi Z_1 Z_2 \right)^2 \approx 500 \; kev[/math]. The overall fusion probability is the product of the tunneling & thermal velocity distribution terms, i.e. [math]P \propto P_T P_M \propto e^{-\left(\frac{E_G}{E}\right)^{1/2}} e^{-E / kT}[/math], which product produces a "Gamow peak" at intermediate energies.

Edited November 26, 2011 by Widdekind

[timo]

The temperature of the Sun is too low for a self-sustained fusion.

It's pretty clear what you meant so take this as nitpicking: There's strong experimental evidence that the temperature of the sun is actually quite sufficient for a self-sustained fusion, at least at the parts of the sun where self-sustained fusion happens .

[imatfaal]

It's pretty clear what you meant so take this as nitpicking: There's strong experimental evidence that the temperature of the sun is actually quite sufficient for a self-sustained fusion, at least at the parts of the sun where self-sustained fusion happens .

nit-picking - but definitely high-quality nit-picking.